Test ride as many bikes as possible. I typically recommend that you ignore price tags at this stage in the process and ride the best bikes in the shop. This will give you an idea of what a good bike feels like and will provide a benchmark for comparison as you look at different bikes. I also suggest you take a friend with you who can go on your test ride (preferably someone who knows how to ride a road bike), since they can help you with the basics like shifting. Take as long as you want for your test rides. Afterall, you,re making a significant investment in your new bike, so you want to make the right choice. Don't let the shop rush you -- you,re making the purchase, not them!
Especially if you're making the transition from mountain or hybrid to a road bike, you want to make sure you get the bike that "feels" the best to you. A road bike will feel "strange" to most people who are making the transition from the upright geometry of a mountain or hybrid, so spend enough time on enough bikes that you feel comfortable with the road geometry. Once you're comfortable with the geometry, you can then differentiate between different frame materials, makes, and models (the last typically dictated by price).
Every bike handles differently, so take this opportunity to ride a variety of frames (titanium, carbon, steel, aluminum) and decide which you prefer. They will all feel/perform slightly differently, so make sure you get the one you like. After choosing frame material, then look at different brands in that material. Once you,ve picked the make you like (ie Trek, LeMond, Klein), then look at different models within that brand.
Any bike can be fit to your body (well, almost), so don't let "fit" influence your decision too much. During a test ride, a bike shop can't commit the time or labor to making your fit perfect. They'll do a quick, initial fit, but the fine-tuning will come after you've made a purchasing decision.
After you've decided on the perfect bike for you, your local bike shop will spend a long time with you (at least an hour, most likely much more), fitting the bike to you (not fitting you to the bike). They can swap out stems, bars, saddles, and components to set up the bike so it's just perfect for you. Don't rush this process and try to make component changes before you leave the shop with the bike. If you are changing anything significant (like the bar), it will take time for the mechanics to make these changes. Be patient -- it will definitely be worth your investment in time.
Women (and smaller men) have unique bike fit concerns because the geometry of most traditional bikes is designed to fit a man. Even the newer WSD (women's specific design) bikes don't always address all our unique challenges as women. Typically, a woman's torso is shorter and her legs (especially the femur) are longer. Our hands are smaller and our shoulders narrower. We even carry our weight (center of gravity) in a different place. So find a good shop that will acknowledge these differences and take the time to address them in your fit. A shorter top-tube or compact geometry, a narrower bar, and shimmed levers will all help make the bike fit your unique needs.
My last piece of advice is don't listen to your male cycling buddies when they tell you they know exactly what you need -- they probably don't have a clue! LOL! Find a good bike shop and let them do their job (sizing, fit, purchase advice). You make a significant investment in a new bike, and that purchase includes a commitment to service by your bike shop before, during, and after your purchase. Let them share their expertise and build that relationship.
