1) Padded bike gloves. Made a big difference for me.
2) Grip in such a manner that the back of your hand is in line with your arm (not bent at the wrist).
3) Don't put the palm of your hand on the ends of the grip (I was bad about this, but it puts pressure on a nerve in the palm of your hand and your finger will go numb)
4) If you're getting neck strain, I'd bet money that your shoulders are tensed upwards and not down and relaxed. That's something I have to work on a lot.

Make sure your bike is properly fitted and adjusted for you. Your legs should not be straight at the bottom of the downstroke (should have a 30* angle), the top of your leg should be less than parallel to the ground at the top of the stroke, and at mid stroke your knee should not be past your toe. Those are some basic tests you can do for your bike fit.