1. Hold a weight isometrically for 20 seconds at your weakest point.
   Then pump out 8-10 reps.
2. Go immediately into a second hold targeting the same point in the range of motion, for 15 seconds. Then pump out 6-8 reps.
3. Go immediately into a third hold, again targeting the same point, this one for 10 seconds. Now do as many reps as possible.

You'll actually feel your muscles inflate after you're done. By the way, the same method can also used for biceps. Do the iso-hold at the mid range of a curl variation.