I used to have the same problem. My pedals would last about 2000 miles, then the inner bearing would fail, which is what makes the cracking noises you refer to.
I finally raised the devil with my Trek dealer about the cheap parts he was selling me, and he came up with a set of pedals made by VP Components.
There are 2 differences between these pedals and the ones I was using. First, the inner bearing on this pedal is a brass bushing, not a ball bearing. Second, this pedal has a dirt/water seal to protect the inner bearing.
I have been using these for at least 15,000 miles now, and they are still as good as new, and they didn't cost any more than the cheap pedals.
If you buy a new pedal, turn the pedal's axel. It should turn with perfect smoothness. If you feel any sort of catching, it is using very cheap ball bearings, and it isn't worth installing on your bike.