Tweetif you get a sharp cramp in your calf when you run it may be because it is not stretched out enough. Also if you are new to running the repetative use of the calf will wear it out quick and it decides to quit on you.
magnesium citrate is the best form of mag IMO very bioavailable. start with 250 mg morning and night and work up to 500 mg each. if you can handle that dose (most can easily) it will help.
potassium is important but is common in many foods and most people are not deficient like mag.
stretch calves good, warm them up before running, compression sleeves help some although I hate em, start out slow and at the first hint of a cramp walk, do not try to push through. that is a good way to hurt yourself.