I draw out my quilt in eq and make a few copies of it as a line drawing. Then I sketch in some ideas that I think I will like. When I know pretty much what I want to do I keep that drawing handy to refer back to.
If there is an element that I am not sure about I sometimes put some press and seal over that area of the quilt and audition my design there.
I try to at least have a general idea what I want to do before I start stitching. I am new at this so I have a lot to learn.