roleplaying tips
1. don't be afraid to do something simple. While having a backstory and all that can help you flesh out your character, it's not always necessary. After all, your character's story should be what happens DURING play, not what happens before you play. (Otherwise, you should just go write a book) If you really need a quick way to build up, here's what you do: pick two emotions. The first one is what you're trying to invoke from the rest of the party members (and will more or less define how the character interacts with them), and then one emotion/thing that truly drives your character. Share it with your GM so he can craft the game around your character. This way, your character will have some pre-baked characterization within without requiring you to write a 20 page backstory.
2. templates are fine. but remember do try to make each template you have count. when you start adding 4 different templates to someone who is basically a human in different skin, it starts looking a little ridiculous. Granted, if your group is all like this, than it won't matter.
3. roleplay and power are not negatively correlated with each other. The only time it does is if being GOOD at what you do actually runs counter to your core concept. So, you can have a powerful character without sacrificing depth.
4. make sure your character can mesh with the party, unless you guys are playing a game that encourages interparty conflict. (Indeed, certain systems THRIVE on interparty conflict since players can play on different sides of the line) It helps to talk it all out with everyone at the table.
Game system stuff
1. 4E is the easiest to learn of the D&D games, and probably has the widest audience right now. It's not my favorite, but it does the job.
2. if you're playing 3.5E, full casters with utility spells will trump all other characters any day. If you're at all concerned with how well your character performs mechanically, don't touch monks. Making those guys work requires quite a bit of a crunching.
3. be careful of splat books. while they certainly have their uses, it's introduction can often be divisive among the party.