Start with five minutes and build up the time. 20 minutes is a long time. 5-10 minute training sessions are great, even for adult dogs.
Always end training on a positive note.
Set up the dog to succeed and praise him for it. The alternative is to set him up to fail and correct him for it. You can get there either way, but the former is more enjoyable.
Heidi Ho, Odie
Joy-Joy, Bear Cub, Hepsi-Pepsi
Cujo2, Karma Chameleon
Ramona the Pest, Kojak -- who loves you baby?
Tiny Tinnie, Susie's Uzzi, Kaiah -- The Baby Monster.