Well sit and lay down are the easiest and most common tricks to teach your dog. I'm no expert but when i taught Ruby how to "sit" the very first time, i had a treat in my hand and raised it a few inches above her nose while i said 'sit' at the same time. I helped her 'sit' the first few times by pushing a little on the top of her bum gently. She got it pretty fast. When i'd say 'sit' and she forgot i would tap my finger lightly on the top of her bum to remind her and she would sit right away.
I would teach 'Lay Down' after 'Sit' because once they are sitting it's half way to laying down. When i taught Ruby to 'lay down' i pointed to the floor with a treat in my hand and said 'lay down' and gently layed her down at the same time. After doing that a few times she was a pro.
Good luck!
