They’re miserable!! You happen to be awake in bed and you feel a cramping sensation in one leg–it’s as if the muscle will break if you bend your leg! Hurts like hell and you can’t stop it.
What do you do? 
I the affected leg vigously. This usually wakes my wife, but fortunately she is a tolerant woman.
What do you do?
Stand on it. Stretch the muscle.
As much as it hurts to do so, you’ve got to walk it off. Otherwise, the agony lasts longer (and it is agony).
I suffer from cramp. If it gets too bad, I get out of bed, stand (on a rug) facing the wall about two feet away and do (sort of) push ups, while keeping my feet flat on the floor. I find that the cramp goes away after a few minutes.
I have seen suggestions that doing this exercise before bed can help prevent cramp, but have no personal experience of that.
The first thing, as others have said above, is to stretch the muscle. Walking around will do this although it’s not the best streching, but what if the pain is so great you can’t even stand up? Stretch it while lying down. Straighten the leg, then flex the ankle so that the foot goes towards your body. Yes, this will be difficult with a cramp, so you may have to slowly work at it.
OK, after the cramp subsides, you’re still not done. It may come back if you don’t do more. Get up and do more stretching. I do a stretch similar to what bob++ suggested, but more extreme. Brace yourself against a wall or counter (counters work better). Put the foot of the cramped leg backwards as far as you can while keeping the heel on the floor. Lift up your other foot and rest it on the back of the foot on the floor. Now slowly move your hips forward and downward as far as you can while still keeping the heel on the floor. Hold the position for 15 or more seconds. Remember to keep the heel on the floor, that’s very important. If you feel up to it, move the foot back further and repeat.
Now something caused that cramp and chances are it’s being low on potassium (at least that’s what it is whenever I get a cramp). So after stretching, I drink a lot of sports drink. Those should be high in potassium. Check the labels to make sure it has at least as much potassium as sodium.
NOTE TO ALL: Read the thread on using soap for leg cramps.
Your suffering days are over ! !
Standing on it, try to walk and stretch it a bit – that works for me.
Reasons for this are: low on magnesium, protein, potassium & veins.
The more cramps I get the worse my veins get, the worse the veins get - the more often I get cramps.
You might try “Slow-Mag” – over the counter product that is what it says, a slow release form of magnesium. It’s worked great for me. If I stop taking it, the leg cramps return.
And if it does not improve after, say, a month of taking Slow-Mag every day, you should consider getting this checked out by a doctor; might be something else more serious going on.
I must say that while this worked for me, this is only anecdotal and should not be taken as medical advice; nothing trumps what you get with real life attention from competent medical professionals.
Get out of bed and stand on one leg, the one cramping, with the knee locked. That usually works for me in a few seconds.
I get out of bed and walk around. Hydration also helps. Also, one of my hypertension medications (Losartan) causes an increase in potassium levels and has led to fewer cramps for me.
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Since this is basically a medical advice question, let’s move it over to IMHO.
Moving thread from General Questions to In My Humble Opinion.
I suffer from the same issue and because of it, I take one potassium tablet a day. It works - at least for me.
If you’d rather, eat a banana a day. I hate them, otherwise I’d do that rather than taking a pill.
I don’t usually have a problem with leg cramps, but I did once and started eating bananas. No leg cramps after that. Don’t know if that’s what did it but it’s going to be the first thing I try.
What do I do? I imagine what my life would be like as Thomas The Tank Engine until the cramp subsides. 
As much as it hurts you got to stand up and stretch your leg muscles by putting pressure of your toes and leaning forward so the muscle in the leg or foot stretches. You will get relief. Include one or two Banana’s in your Diet daily as this will help. Good Luck!
I lie on my back and point my toes toward my head.
If it’s a calf muscle, I stand up and stretch the muscle by bending the knee on that leg, keeping my heel on the floor.
When I’ve had calf spasms, I discovered this trick, which has always worked immediately & well for me. Doesn’t matter if I’m laying on my back or side or whatever position, as long as I can point my toes (whole foot, actually) toward my head like that.
I typically had these spasms while in bed half asleep (or more than half asleep), yet I once I discovered this trick, I always had enough presence of mind to do it.
BTW, the proper anatomical name for the calf muscle is the gastrocnemius muscle (pronounced, AFAIK, just like it’s spelled – there are no silent letters there).
This works.
Any tips for foot cramps?