I also recommend use of Morton Salt Substitute to help get potassium. USE IT WISELY! I was getting the same cramping (no, I can't have the other kind! LOL ) until I adopted its use. I use 1/4 tsp with a packet of splenda in a glass of water both in the morning and in the evening.

I have also made sure I supplement both calcium and magnesium. Sodium doesn't seem to be a big problem for me to get so I don't suppliment that unless I am putting a couple hours or more on my bike or unless I notice I have put out a lot of effort during the day.