Go to gun ranges and rent the firearms that they have. You'll get a good feel for what you like and what feels good in your hand. Some people carry larger guns, some carry smaller ones. I switch between two different guns depending on winter or summer carry, I carry a larger one when it's colder due to it being easier to conceal under a coat. Summer carry you will want something a bit thinner to help conceal against your body, should you decide to carry IWB (Inside Waist Band). Make sure you know the laws of your state and any surrounding states that you may enter. Ignorance of local laws will not get you a slap on the wrist when it comes to firearms. You should check out the firearm thread to see what guns other members here have, it'd give you a good idea of what you might be seeing. If you're under 18 then most gunshops will ask you to leave or to return with a guardian, some may not let you shoot pistols unless you are 21. Call around to the local gunshops to find out their rules and check out their websites if they have one. Don't let people tell you what you like, make sure you make that decision. Lastly, make sure you can afford it and that you are sure you want that gun before you buy it, even if you buy a gun new and never fire it, the best you might be able to do selling it back to a gunshop might be half. So be certain of your decisions and remember the four rules of firearm safety.
All guns are always loaded. (Treat them so!)
Never point the gun at anything you are not willing to destroy.
Keep your finger off the trigger until your sights are on target (and you have made the decision to shoot).
Be sure of your target and what is beyond it.