In general, warming up your muscles only requires performing the movement with lower weights. It's fine to use sets of 5 and then taper off the closer you get to your work weight.

However, if you are having pain in your hand, I would check your form. Is that pain shooting up from the elbow? If so, it's possible that you are putting too much strain on that joint and have developed a bit of tendinitis.

Make sure you are exercising the muscles you think you are. For example, if you body is swaying just to get the bar up while doing barbell curls, you need to strengthen your core before you can improve your biceps--which in general is not a bad idea.