The best way to ensure that you get a good pup is to go with a good breeder. All puppies are cute, but health and temperament are genetic, and the breeding and background of the parents is what is important.
It takes a lot of knowledge, dedication, and planning for a good breeder to be able to make good breeding decisions, so picking your breeder is more important than picking your puppy.
Start by telling us what you want in a puppy, which lines appeals to you the most, what your goals and plans are, what area you live in. People may be able to give recommendation on breeders, and in the mean time, there is a lot of reading here on the forum you can do to educate yourself.
You can start reading stuff here, and ask questions on the board as they come up through the process of learning more:
How to find a puppy!
Welcome to the GSD/FAQ's for the first time owner - German Shepherd Dog Forums