Go to the LBS. Test rida a lot of bikes. Go out of town to another set of LBS and test ride a lot of bikes. Listen to what everyone in the shops are telling you and try to determine who knows what their talking about. (that is the hard part.)
Think about what you have learned and go back and test ride a lot of bikes.
I agree with Stapfam, your first road bike may not be your last so plan accordingly.
Did I mention that it was a good idea to ride a lot of bikes?