I tend to make my own, although for a few projects I have followed patterns. For this reason, I prefer "block pattern" books to books that give you patterns for whole quilts, because I just never use the patterns, though I may use pieces of them. I read books and magazines mostly for inspiration.
I never make a quilt exactly from a pattern with all the same (or similar) fabrics as shown in the pattern. Even when I follow a pattern I usually end up changing size or border widths or something.
I use a lot of graph paper. :)