Here is good instruction from deWalt.

If you have a miter saw, take a look at the miter 38. some degree, they
are marked a little darker for that perpose, I did not know this myself
till I had to install some molding two weeks ago and I had the miter
saw for 10 year.

http://www.dewalt.com/us/articles/ar...odworking&ID=2
hope this works.
Max