I would out wait him. He's gonna wanna get up eventually.......LOL

Make sure you use lots of yummy treats and fun toys. Make the leash a fun thing. Don't try to tug or pull him where you want to go, no matter how gently.

Use lots of praise, lure him, get him to chase a ball, whistle, clap your hands, talk in a squeeky voice, anything to get him up and interested in what you are doing. Don't give in and take the leash off when he lies down. Then he has won.

Above all, remember.....have fun!

Good Luck.

Here's an article that explains it better than I did. You have to scroll down a bit:
http://www.perfectpaws.com/cls.html