Another clay bar tip is to tear the clay bar into multiple pieces. Of course, this all depends on the original size of the bar. You may only get it into 2 usable pieces.

The reason for this is that if you drop your clay bar on the ground you do not have to risk trying to use it with pebbles imbedded in it. You can then go with your backup piece of clay. If you've ever dropped your clay bar you can appeciate this.