Now that you've competed the game, it's time to get down to the grind.
You'll have to do everything with all three characters. The only exception is Rumble Racing. After getting 1st in all of the Rumble Racing tracks in Disney Town, you'll unlock them in the Arena for all three characters. So, you only have to do those twice with one character. Otherwise, you have to do everything with all three. Aren't you excited?
The order in which you do the reports is entirely up to you. Most people find Ven the easiest and most enjoyable to play while people find Aqua slightly more difficult to use but still not too bad overall to master, and Terra is almost always said to be the most difficult and least enjoyable character to play as because he's much slower with mostly everything and has more trouble during boss battles.
This can be a bit daunting, so just take it one section at a time, and you'll be done before you know it.
Just a note, if you haven't gotten 
Perfect Shot by the time you've beaten the game, be sure to be using your shotlock. You can grind it out if you want, as you only need a single hit for it to count, but it's easier to just use it as you're going for commands, or when you're in the Arena. Keep in mind that you'll also need to use each shotlock at least once to complete the Hit Counts section.
Chests -No matter which character you choose, the first thing to do, is to collect all of the chests and all of the stickers. Keep in mind that revisiting Land of Departure with any character at this point will require you to defeat the boss Mysterious Figure (refer to 
Time's Teller for more information), which is best saved for last. Getting the chests will cut down on the materials you need to create commands, as well as find some commands that you would've had to make otherwise. And the stickers will unlock the DJ Mixer Command style (Which is probably the best in the game). Head to The Adventurer: Terra, The Adventurer: Ventus, and The Adventurer: Aqua for chest locations for each characters. Then head to Collector for sticker locations for all three. During this step, you'll find the Break Time command, so be sure to use it with each character for their individual Break Time trophies.
Disney Town Mini-Games -After finding all of the chests and stickers, it's time for some mini-games. These also give special commands that will save you some time later on. So, head on over to Disney Town. The first character you're using will have to do Rumble Racing, and come in first on all of the tracks. Which will net you the Rapid Racer trophy, and unlock all of the tracks in the Arena. Once you've gotten that done, head over to the Fruitball court, and scroll down to take a look at Fantasista for a strategy on how to win. After beating all of the Fruitball opponents, it's time for the Ice Cream mini-game. Head down to Maestro for more info on the game. You'll need to play through both versions of every stage with all of the characters to complete the reports, but only need a Fantastic rating on all of them once.
Abilities -During the command collection step, you'll want to work on getting all of the abilities as well. If you don't have all of the abilities by the time you're done, you can clean them up when in the Arena. Just try to make sure you've got as many as possible. An easy way to train abilities fast quickly is to head to Neverland. In either the Gully or Peter's Hideout (depending on the character) there's a moogle shop. You can use this shop to buy commands you need quickly. Be sure to sell any commands that are maxed out, that you don't need. Anyway, walking in and out of the area with Peter's Hideout is a great place to level up commands. Especially if you use Experiment 626 while maxed, as you earn double the cp. Doing so, you'll be able to max out most of the commands in just one or two of the mobs. Make sure to revert before you use Experiment 626's finisher though, because it takes a ridiculously long time. If you revert before picking up the D-Link orbs on the ground, then you can just immediately go back into the D-Link, and always have the double cp.
Finish Commands/Shotlocks -While collecting your commands, you should also be going for getting the Finish commands completed. Head over to The Warrior: Terra, The Warrior: Ventus, and The Warrior: Aqua to check out what you need to do to unlock each of them. Also make sure to be using each of your different Shotlocks to complete the Hit Counts part of the reports. If you don't have them finished by the time you get all of the commands, don't worry, you can clean up the rest in the Arena.
Ice Cream! -Now that you're done hunting for commands, there's one more thing that needs to be done before starting on the Arena. Getting all of the Ice Cream flavors. Head over to Pâtissier for the locations of all of the ingredients, and what you need to make all of the Ice Cream. There are a couple that can only be found in the Arena, so leave those for now. Be sure to get the rest though, because you get a lot of EXP for defeating the Unversed that drop ingredients.
Unversed Battle Missions -These missions are similar to the Organization XIII Mushrooms in Kingdom Hearts II Final Mix. You play a little mini-game, and if you get enough points, you get a reward. These are much easier than the Org Mushrooms though. Head down to Savage Slayer for strategies on how to beat each of the Battle Missions.
Arena: Overview -There's a lot to do in the Arena. To complete this section of the reports, you'll need to get 9,999 medals, complete every arena match at least once, win 7 command boards, and do each of the Rumble Racing tracks within a certain amount of time. It's recommended that you do the mini-games first as you'll need to do them to unlock later Arena matches anyway. So, you might as well get them out of the way. They will also net you some medals to start buying some of the Arena-exclusive commands. It's recommended that you go for the shotlocks first, followed by the most expensive commands. You get 2,000 medals from defeating the final Arena battle with No Heart, so you'll be able to use those to clean up the cheaper commands.
Arena: Command Boards -It's recommended that you start with the command boards first. You need to win a total of 7 times. It doesn't matter which board, but you have to play on all 6 of the currently unlocked boards in order to unlock the final board. Luckily, you've already played on the Keyblade and Royal boards when going for the exclusive commands. So, you just need to win on the other 4 to unlock the secret board. In the arena, you can choose the number of players, so always make sure to always choose 2 players. This will make it much easier to win. As the real secret to command boards is abusing your "Hand". Using double rolls and stuns are far more helpful than placing commands and hoping the computer lands on them. Especially since when there's only one enemy player, using stun means you're the only one progressing. Throughout this little adventure in board games, make sure to always try to land on the special panels (the purple one with stars). Doing so will have a random chance for Pete to show up. Which is what needs to happen to get the Pete D-Link. Which is needed for the trophy, as well as completing the Hit Counts section of the reports. Which will be touched on later. Even after winning 7 times, if you don't have Pete, keep going. Just do your favorite/the fastest board just going for the special panels until you get him. You'll be getting medals for playing at the very least.
Arena: Racing -After you're done with the command boards, jump on over to Rumble Racing. You have to do 5 laps within a certain amount of time on each track. No changing that to make it go faster. However, you can change the number of players. Slide that number down to 2 so that you don't have to worry about a bunch of computers messing with you the whole time. Also keep in mind that you don't have to win, just complete the courses within a set amount of time. So don't worry if the computer decides to cheat and zoom past you at the end.
Abilities/Shotlock Cleanup -We're about to start fighting some actual battles, so now is the time to check and see which abilities and shotlock hit counts you still need. So that you can work on them while battling through the arena.
Arena: Battles -Finally! Some action! You'll just want to fight your way through each of the battles. Doing so for the first time will unlock Pawn of the Arena, Knight of the Arena, Queen of the Arena, King of the Arena, along with Keepers of the Arena, and by the end of all of that, you should have unlocked Villains' Vendetta and the Ultima Weapon as well. Unfortunately, you more than likely don't have enough medals to unlock Eraqus' Armor or the No Heart battle. So, it's time to grind. Monsters of the Sea is an excellent way to farm medals. Just use a Mega Flare to instantly clear the first round. After getting on the wooden platforms, quickly attack 2 explosive barrels to throw them to Monstro. Two hits will stun him. Afterwards, swim/glide to his tongue and unleash 6 Mine Squares to inflict massive damage. It's recommended to have the Rhythm Mixer command style (seeD.J.for more information), because that one will quickly deplete Monstro's remaining health. You can complete the challenge in 50-60 seconds, earning you 675 medals. If that match is too hard anotherway would be to have 4 Mega Flares, and doing Risky Riches over and over, which nets you 70 medals in about 25 seconds. You can just play whichever match is the easiest too. Doing other matches will net you more EXP, if you want to level up as well. Once you get enough medals to unlock Eraqus' Armor, go ahead and fight him. Head over to Light's Will if you need some help defeating him. After that, you'll have to head back to grinding to get 9,999 medals and unlock No Heart. You can take a break and skip down to do some cleanup first, or just grind it out in the Arena. Defeating No Heart will get you the best keyblade in the game, Royal Radiance, which will make defeating the Mysterious Figure/Unknown easier. Head down to Darkness's Will if you need some help defeating No Heart.
Command Collection -Now it's time to collect all of the commands, and work towards getting all of your abilities. Doing this first, makes it easier to complete the Arena, because the Arena has the most powerful monsters, and by the time you're done with making all of the commands, you'll have gained at least a few levels. Head to the synthesis guide to check out how to get each command. There are some Command Board specific commands you'll need to get as well. To get them you have to play the boards outside of the Arena. As they do not show up in the Arena command boards. Luckily, there are only 3 exclusive to the command boards, and they're on the boards Keyblade (Ragnarok), Royal (Meteor Shower), and Spaceship (Lightning Ray). Everything else can be made through melding. Remember, you don't have to win in order to keep the commands, the game just has to finish. So, feel free to just run around in circles until you get it. And if the computer gets the bonus panel first, just quit the game and try again.
Vanitas Remnant -Now it's off to defeat the Vanitas Remnant. He's actually painfully easy using the Strike Raid exploit explained in A Mere Shell. Feel free to do him earlier if you'd like. Especially with Terra, as the keyblade you get for defeating him gives a large boost to Strength.
Mysterious Figure -Some people think this is the hardest boss fight in any of the Kingdom Hearts games. Rumor has it that the developers were never even able to beat him with Terra. Head on down to Time's Teller for the strategy you could use to beat this monster of a boss. After defeating the boss, do not forget to open the chests in Land of Departure. Leaving the world means you have to defeat the boss again to access the chests.
Clean up -At this point, if you were keeping up with everything, your reports should be complete. If you missed something, check your reports to see what you've missed. The most common thing missed, are the Hit Counts. You'll need to use both finishers with each of your D-Links. One from when they're maxed out, one from before they're maxed out. If you've gotten them maxed out before getting the first finisher, don't worry, you can just go into the menu, choose D-Links, and set which finisher you want for each individual D-Link. Also check your shotlocks. You need to use each one at least once. Another common thing missed, is the Blobmob unversed. It spawns on the Deep Space world, in the same room as the Gluttonous Goo Battle Missions. If it doesn't show up, make sure to kill all of the enemies. Sometimes it doesn't show up until you've killed everything else. Also, every time you kill it, it splits in two, until there's 8 tiny Blobmobs. Make sure to defeat them all so the Blobmob shows up in your reports.
Do it again -Repeat this process two more times with the other two characters.
