The hamstring stretch is good because it will loosen up the muscles near the sciatic nerve that are tight and may push down on the nerve.

Lay down flat on your back.  Slowly lift one leg up to your chest with your knee bent.  Using your hands to support the leg, straighten it out as much as you can.  As always, do not stretch it too hard – you do not want to inflict pain or cause a muscle strain.  Hold this stretch for about 20 seconds, then put your leg back on the ground and let it relax.  You want to do this stretch at least three times for 20 seconds each.

A slight variation of this sciatica stretch is to lay down flat on your back and to lift one leg as far as it can go.  This time, you do NOT want to bend the knee – keep the leg straight at all times.  You will want to use your hands to support the leg.  Again, do this stretch at least 3 times for about 20 seconds each rep.