If you fold your fabric, it's very important that your folds are even, and that your ruler is at a 90 degree angle from the fold.
Check every so often to make sure that your strips are still straight.
I prefer to buy 1.25 yards and cut parallel with the selvage for my long strips. I figure the strips should be on-grain in at least one direction.
Also, what QuiltnNan said - when the fabric is folded selvage to selvage - there should be no pull/fold/drape/crease lines - shift the ends until the piece is flat. (I've always had a problem knowing how to describe that - but it is THE MOST IMPORTANT step in folding fabric for cutting.)
Last edited by bearisgray; 07-28-2012 at 09:48 AM.