If you have never read it, The Curtis Creek Manifesto has an excellent section on leaders, that helped me greatly understand the purpose, and the functionality of a leader. First and foremost, you need to have some sort of taper in your leader, whether its hand tied with leader material, or packaged.
I would say go to the fly shop, and pick up a copy of the Curtis Creek manifesto if you haven't already done so; if they don't have the CCM, consider finding a new fly shop.
For the Record, I am a packaged leader type of fellow, because I hate the idea of relying on three or four extra knots that I tied when I hook up with that trophy rainbow.
Everett