You should look into rescues or the humane society in your area. They'll have a better idea about the dog's behavior and obedience. Some small dogs are perfect angels and some can be beasts so it's good to know that they've been somewhat worked with and they get to know 'em.
*random* Don't get a beagle. Their bark/howl will drive you crazyyyy. Lol. It all depends on what you are looking for. A lot of small dogs are high maintenance. Yorkies are smart and catch on quickly when it comes to being trained. I have a yorkie and he was completely trained within 2 days of getting him. My chihuahua on the other hand, is NOT as smart. It took her over a year to learn to sit. And she still isnt fully potty trained and she is almost 3.
I work at petco and see so many dogs and personalities every day. Good luck in your decision! So exciting!