Ride bikes, lots of them. Ride stuff that you think you'll love and stuff that you think you'll hate. Ride different sizes of the same model- you might be surprised by what feels right. Ride stuff at all price points. Is the $5000 bike twice as good as the $2500 bike, or does the $2500 bike feel just as good, but have slightly heavier components?

Every bike that I've ever owned has helped me further define my preferences, even if one or two have turned out to be the wrong bike. While I'd have preferred to get it right every time, the experience has been invaluable.

I agree with those who suggested going with a stock bike if the fit is right and working on the shifting skills. It quickly becomes second nature.