Go all out Evil or all out Good. It'll be a pain in the ass when you want to go for the trophies if you mixed it up. I haven't played evil yet, but I'm guessing that good is the more satisfying ending.
Go for the Dead Drops at least, before you finish everything on each island. I haven't gone crazy collecting the blast shards. I plan on collecting them all in my second play through as evil, with a fan made map to help me (if one is avaiable...) like I'll do with GTAIV. Constantly press L3, and go for the dead drops. There's only a few and they're rewarding to listen to.
Get the good/bad upgrades first, because I upgraded the neutral skills, and now I have to go kill some baddies to get XP to upgrade all my good skills (and it doesn't help that I made the entire world crime free...)
Recharging on wires/train tracks is extremely valuable though.
