There is such good information in the Blog Post I shared awhile back from Baltimore Dog Works that I wanted to share a segment of it again. The only thing I would change is Rarely test, rather than Never test.
ALWAYS TRAIN, NEVER TEST
Tests are fine for kids in school. Not for dogs. Whenever you are with your dog, get it in your mind that you are not testing them to see if they are going to do the right thing or the wrong thing. You are, instead, going to give advice and guidance... as much as necessary, but as little as possible... always. This is an important thing to get in your head. I've said this in front of group classes before and literally seen an immediate change, a softening in handling, a release of tension, and an overall more understanding attitude from clients. The actual actions (leash pressure, corrections, praise, everything) don't actually change. But the attitude and the vibe the person is giving off makes a major difference to the dog.