This is a big decision! We like to think of having a dog just like any other relationship in your life. The main difference, however, is that once you choose your pup, you're making a lifetime commitment to them, just as much as they are making a lifetime commitment to you!
Once you've made the choice to adopt a puppy, what's next is to pick the right one for yourself/your family. Consider your lifestyle (among other things) and compare it to the breed you're going for, and what they're bred to do. You can even find Facebook groups for that particular breed, where you can learn from other pet parents familiar with the dog you'll be bringing home!
Once you're set on a breed and you've found a litter, see if you can meet the puppy's mom and dad and/or learn as much as you can about their demeanour before selecting from one of their pups.
As you learn about them and get to meet the pups, from your first impressions you can often get a good idea of their energy level, demeanour, and even personality to see if you think it will be an ideal fit for you, your personality, and your day-to-day life!