Just a reminder, if you guys want to train your Yorkie or any puppy to do tricks, I suggest between 3 months to 4 months is the best time, from my past experiences. You can teach them thins using good treats, teach one thing (in one day-about 30 min of consistant and persistant training) and practice it for a week or two. Then teach another thing. For example, first thing is "sit", right? You take you puppy when he is slightly hungry time, take some good treats (cut them up small into about 15-20 pieces, so that he doesnt get full and doesnt' want to listen to you anymore) and take him into a quite room with no distraction. You tell him to "Sit" with a hand command also. He will not know what you want him to do at first. You keep saying the same thing and gently push his butt down to sit. Do this about 10-15 times, He will surely sit on his own on command. It's a patience test for the human. ha ha ha.
I taught Maximus everything he knows at 3-4 months except playing dead (he learned this at 6 months and believe me, it was a LOT harder to teach at 6 months). Here are commands he will listen to and do: No, bad dog

, good dog

, No potty, bad potty, good doggy potty, potty, ok (from time out punishment), No more (food), Go get him Max (barks on command), Go get the ball (fetch), sit, hand shake, lay down, stay, come, go, bang (play dead). I still have not taught him how to roll over. I should soon b/c I know it will get harder and harder.
If you want your doggy to do certain things (since you will live with him for many years to come), now is the time to teach him all you want, when he is still a puppy!