I need so much help on choosing a bike TOMORROW... I seriously do not know where to begin and I am so darn new to this. Basically, when I enter the shop I don't want to seem like a total arse, and chat crap. I want them to think I know what I am talking about. plus I am in a dilemma of deciding what sort of bike to get. To be honest I wasn't aware there were so many options, because the bike I have now was a hand-me-down, and I just use to get to places. But now I am thinking of getting one to start learning street/land tricks BUT AT THE SAME TIME I want to be able to ride my bike as a normal bike to get to places. I am so shite at all of this, and this is where you guys come in.

tell me loads of stuff about bmx bikes, like gear ratios ect
Would a ratio of 28-9 be okay to ride it normally on the road.
How light do I want it? (by the way, I'm a girl that's like 5 ft2 and weigh like 6.5/7 stones....does that have anything to do with it? see? I have no clue)
inform me of all the valid points I need to bring up, like the right questions, and what to look for tomorrow. I REALLY DO NOT WANT THEM TO TAKE ME FOR A RIDE and think I am easy bait.

Okay so that is it for me. I am sorry to ramble on so much... but hopefully you understand where I am coming from. Anywho... I will include forever in my prays and good wishes and rate your answer.

Thanks so much.