I prefer to cut lenghtwise if I have enough fabric. Fold it so that it is squared up - no ripples in the fold line. Make your first cut (to cut off selvedges) a generous cut. Before you make another cut - pick up your first cut and check each fold line to make sure you don't have the dreaded V. If you do, re-fold.
Cut one piece at a time, check each piece for the dreaded V before you cut the next!!
And use a brand new rotary blade.