i choose my main by playing as all of the characters and seeing who i like the most ex: jade, sub-zer, and rain from mortal kombat.
prince of Persia moveset: http://community.us.playstation.com/t5/PlayStation-All-Stars-Battle/Prince-of-Persia-in-all-stars/m-p/38273897#M125640
2. I like agile characters, the all over the place types, I also flashy high exacution comboer, cause doing combos is really fun, also competitvly, my main strategy is counter strategizing, like if I know people are gonna do lvl 3 x-factor shenannigans in mvc, or run a rain team in pokemon I am prepared and can counter it, or playing the blue color in mtg I notice that when you take away your opponents favorite toy, their teams or gameplan falls apart.
In free for alls I will probably play a variety of characters, but if I wanna win I will go with cole or ratchet, competively probably dante or sly, cause dante is known as a jack of all trades and has been known to have tools to deal with anything, and sly can dodge and evade people's attacks and supers with ease, he can also steal AP from people, taking away their ability to perform supers, and well how can you win without supers? =P
I'll grab a small group of characters I like based on personality, and play them 'til I find one that suits my playstyle.
For the most part, though, I just play EVERYONE. Even in League of Legends I play almost all the characters...
If idiots could fly, this forum would be an airport.