I can't stress this enough: Adopt older dogs.
The shelter thought that she was around 8 and said "give this sweet girl her retirement home!" Considering that we were first-time dog owners, we thought that a chill dog was what we needed.
She runs circles around us, even after three years. She's never had an accident in the house. She loves kids. She never leaves our sides.
And two weeks after we brought her home, she alerted me that I was going to have a seizure. She still does this.