My tips for getting rid of the dreaded V cut.
1. prewash the fabric to get rid of the manufacture "center" crease. I suggestthis because badly folded fabric will "remember" and go back to that crease , and you will need to fight against it for all of your cuts.
2 The refold selvage to selvage . make a "new" not hard center crease. ( note at this point it is very likely that the raw edges will not at all match up, that is the purpose of this step to re- establish a new correct line). The fabric should lay flat selvage to selvage. It is usually easier to do this allowing the selvages along the entire fabric to hang perpedicular to the floor.
3. Line both selvages along a horizontal line on the cutting mat.
4. At this point you will most likely see the raw edge is at a diagonal showing how it was not straight to start.
5. Using your ruler make a perpedicular ( 90degrees from the selvage) cut to square of the raw edge.
6. Use the new edge as your starting place for your strips, keeping equal pressure on both the ruler and the cutter all the way through cutting of the strip.
Note : sometimes when cutting the person cutting lets up a bit on both the ruler pressure and/or the cutter at the end of a long strip. this will give a smaller V depending on how much the ruler and or cutter was allowed to "drift" at the end of the cut.
When I got my first rotary cutter I was making V's and W 's. I think we all have done it more than we like.