For Role-playing :Start simple; for your character "personality" use some obvious, cliche gimmick like the ones you see in the movies/game/novel. Then appliy you own ideas/twist on it. That way you already have non-verbal quirks you can use, and some guidelines as to "how would GROK the Barbarian react to that strange situation?"
Just playing "myself, but with a sword" is kind of boring. But, frankly, nothing wrong with it.
Dont forget; you play the game to have fun. To have fun with your friends too. Its not a competition of the GM versus the player, its the opposite. If you like something about the game, say it. Want to try something? ask for it. When i DMed, i was quite happy when my players gave me feedback on what they liked and what they didnt.
For Character build:
In 3.5 i like the cleric and rogue.
Cleric keeps your friends alive and fight very well, and you dont have to walk around in robes or whatever, you can run around in plate armor if you feel like it. The spellcasting is reasonably simple (dont pick healing spells, the cleric can transform any spell he has into a healign version at no cost).
Rogues are my favorites; pure distilled flexibility. Not that much HP, they need to keep the flanks and use their sneak attacks often in combat. SO many skills they are invaluable in pretty much all scenarios from dungeons diving, infiltration, robbery, con artist.. you name it, the rogue can do it.
The mage and sorceror are vey fragile early on, and they dont get much in the way of skills. Long term they are nice. Early on.. choose you spells wisely. Try to figure out a plan with your teamates.
Fighter and barbarians.. just are themselves. Very simple. Fighter can have more armor, barbarian is a damage dealer with tons of HP.
RAnger is kinda like a fighter but with more skills. Never used so i dont know.
Monk, never used. But is basically a self-sufficient, loner fighter.. good damage dealer too.
Paladins are good fighter, with good support abilities and spells (lay on hands is a lifesaver!). THe only problem is how badly misunderstood their "code of conduct" is in general.
Druid: can be a good choice; like the cleric you fight well, but instead of healing you can summon plenty of critters to help in combat (more targets and flanking bonuses)