I know good tactics, not for trunks tho i never use him. I just don like his hair (saiyan without black hair = :S) anyway I know good tactics for Buu. Buu starts off with the highest PL of all characters and with mouth blast you can easily win a ps against kamehameha or anything when those characters start, what happens tho is the other characters gain pl faster / transform faster so then you have a disadvantage if you are buu. thats why you need to be a good meleer, hit them with melee and then turn them into donuts, donuts give you 1,000 pl, and if you get low on health turn them into cookie. Never turn them into a chocolate it doesnt do anything except restore your ki and you can do that by yourself. really the best tactic with any character is shoot beams from far or melee and then when they are down hit them with beam (candy ray if youre buu) or ki blasts. Once you make a ki blob use generic beam and explode it so they are sure to DIE. and dont anyone dare say that is dirty tactics either, its fair in every way. I never attack people while they transform or when they are in a ps unless they do it to me.
Now for Vegeta same thing melee people and use gallit gun while theyre down because it charges fast.
Oh yeah and for buu if someone is meleeing you alot you can always block and then there is a few seconds where they cannot attack so you use that time to candy ray them lol.
Some good melee tactics:
avoid people with lower ping than you if you can (lol!)
block and then hit them as soon as you block (unless they tele)
use the swoop hit and teleport away and swoop again on people who block too much, teleport and swoop from different angles this way you can hit them even if they block. and if you hit them and they block it teleport AWAY FAST so they don hit you bak.