I'm trying to look for a road bike and I have no idea where to start. I'm 6 foot, so I'm not entirely sure the size of the frame or anything like that. I know I want a drop handlebar, and many people say that carbon frame is better than aluminum. I'm not looking for anything expensive, possibly 500 and below, and is there any types around that range, (willingly to look on craigslist and such).

Any tips will help either in helping me determine what type I want or help me in finding the right one (parts / style / so forth)