Try out several models of pistols, some places will have demos for you to try. See if some of your freinds have a pistol they will let you try out.
Get the pistol that is right for you, make sure it fits your hand properly.
For self-defense, don't go below .380
Something to consider is price & availablity of ammo. 9mm is the most abundant & reasonalby priced bullets out there.
If you are new to pistols, get a .22 revolver to get comfortable with then move up.
Glock, Ruger, S&W, Sig are all excellent weapons.
Believe me, you will need to practice. Once or twice a year isn't going to get it. You may never be put in a position where you will have to use deadly force but you never know. If you are ever in that situation, you are going to be super-charged with adrenalin, you will be sweating bullets, you will be so tense that you may not be able to think properly.
A little practice and some training, your odds of coming out safe, and those you love, will be greatly increased if ever you get in a situation where your life is threatened.