The books One Block Wonder and One Block Wonders Encore (the one I am using) explains what to look for. You need a sizeable repeat pattern, this fabric was 18 ins repeat.
The quilt (before borders) is approx 48" sq.
The bigger the pattern repeat the more variation of blocks you will get. I putting one together now which has a 24 ins repeat and more colours. You need six repeats of the pattern (plus I got an extra half metre for "whoops I cut it wrong" mistakes.