Think up a hero, create a cool history for him, and figure out a personality. Then whenever you say something, try and make it sound like he's the one saying it. Basically, pretend like you are your hero.
Be as generic or creative as you want. I don't roleplay, but I've teamed with a lot of people that do. I've seen everything from the generic hero spouting out bad puns during combat to a guy who roleplayed a super-intelligent cow(kept talking about grazing) to a troll turned good spouting out puns during combat. Its important to realize when you're just pissing off the team, though; while a good roleplayer is a hilarious and enjoyable addition to any team, if you take it too far it can get kind of annoying. Try and avoid saying little catch phrases each time you use a power, that tends to get old fast.
