Now that your dog knows how to Sit and Lay Down, a good command to teach next is Stand. This command is more helpful than novel. Keep in mind, since standing is such a normal thing for your dog it may be difficult for him to understand why he is being rewarded. Sometimes it helps to click him as he stands up from a sitting or laying position. This will help him realize that it is the standing up action you are looking for.
Step 1: Have your dog lay down. Wait for him to stand up. When he stands up, click and treat. Repeat this action several times until he learns that he has to stand up in order to get his treat. Standing is so natural that it is likely that the dog won't immediately understand why he is being rewarded, so it may take more repetition than usual. (Initially, it's okay to click even if he isn't standing perfectly; you can work up to this gradually).
Step 2: Begin to introduce a visual cue (like your hand gesturing upward) and a verbal command ("Stand") so that he can associate those with standing. Click and treat.
Step 3: Have him lay down, then say, "Stand." Jackpot when he stands in the perfect position on command.
OUR EXPERIENCE
When Caspian learned to stand, I started out having him lay down. I waited until he stood up. While he was standing up, I clicked and treated. Doing this several times, he soon learned that he had to stand up to get a treat. I started using my command (Stand!) as I had him stand up. Soon, he would stand up when I gave the command. I did this in other sessions in Down positions as well as Sitting, Playing Dead, etc., to give him different scenarios for his new trick.
TEACHING TROUBLE
Tip: "Try to keep commands to one or two-syllable words. These are easiest for dogs to identify."