There are 3 resources for how to use Vernier Calipers.
1. Link on how to use Vernier Calipers. There is a flash animation that allows you to adjust the calipers, and have it read for you. Although it does not get the significant figures perfectly correct, it does show how to use the Vernier scale properly.
http://www.physics.smu.edu/~scalise/apparatus/caliper/tutorial/
2. Link to video on how to use Vernier Calipers: approx 6:10 long
http://www.youtube.com/watch?v=ZUNoWWw6V10
3. The file below is a written description of how to use Vernier Calipers, and it has sample problems at the end of the section.