Thank heavens! Someone who is doing research about owning a dog BEFORE she buys one!!! You'll do well.
The pound, the paper and rescue groups are probably your best bet. The rescue groups will rescue pure breds, but they will also rescue mixed that have their breed in them. So, if you kind of have a breed in mind but really want a cute ol' mutt, then consider them as well.
It's not a bad idea to research the breeds anyway. If you are looking for a calm, even tempered dog, who will lay around and let you pet her, you probably want to avoid a border collie mix. If you want an active, playful, frisbee catching (over and over and over) dog, that border collie mix might be right up your alley.
I own an Australian Shepherd and he's a sweetie - kind of a Border Collie with an off switch (he will lay down and relax). He's smarter than I am, though, and I have to make sure he stays busy (mentally and physically). My DH has perfected the technique of tossing the ball while sitting with a glass of wine - it helps a lot.
Lab and retriever mixes tend to be good bets - they are the sweet "dumb" dogs (I say "dumb" because they are smart, they just have that dumb dog expression), who love people and are generally good with kids. But they are also fairly energetic.
That's just a sampling, but they are the mixes you'll see most often.
Shots - well find a good vet and he/she will keep you up to date on what shots are required - if you adopt from the pound, chances are the shots will be given before you pick her up.
Find a good trainer. One who uses a clicker and food as reward - positive reinforcement - if you practice diligently, you will have a dog who is thrilled to listen to you because every time she does what you want her to do, there's a chance for food. Plan to spend 1/2 an hour a day training at first. Believe me, the effort is worth it. People tell me I have such a well behaved dog. It's the effort I put into his early years. I think this point is the most important one - if you trainer her right and give her a positive experience while doing it, you will have a wonderful companion.
Oh - yeah - crate training - consider it. You'll both be happier.
And if you like to read - read Culture Clash by Jean Donaldson - great book and helps you understand dogs and how they think and relate to us better.
Okay, I'll shut up now... Good luck Shelley!