If you can create your own patterns it's a great thing. A stained glass pattern, to me, is like a childs drawing, the pieces have to be large enough and they all have to connect. But it has to be designed to have strength, also.
But, if you would rather have a ready to go pattern there is a great website called glass campus that has free patterns and also links to other websites that have free patterns.
This website also has good tutorials for everything pertaining to glass.