Making sure your fabric is on the straight of the grain before you start cutting length way is the most important thing to do so that the print doesn't start going on an angle. All to frequently we can easily forget this important step before we start cutting a lengthwise piece of fabric. If both of the salvages are lined up start at the outside and make your strips this way you will have a full piece left to the middle that can be used again.
Also be sure to cut a little extra, At least the width of your strips plus 2" if you are mitering the strips.. Have fun doing these strips.