My doctor told me to put the ball of my foot against the wall and press all my weight up against my shin (like a shin stretch, toes towards your shin) it feels sooooooo good!!!! I hate leg cramps :( Water and bananas help, too!
As soon as you start to get one stand up and put as much weight as you can on the leg. I have no idea how come this works but I have gotten the worst leg cramps since the very beginning (im now 38 weeks 4 days) and this is the only way to stop them. Also add more magnesium and potassium rich foods to your diet. Good luck :-)