A reliable source of information is www.mayoclinic.com. Put the symptom in the search box. Night leg cramp is discussed, with the usual treatments. Muscle cramp is much more complex as to its causes; unless it is the usual type due to muscle strain, see a specialist.

I have night leg cramp occasionally. It is common as one gets older.
My doctor, for age symptoms, prescribes calcium-magnesium supplements (with trace zinc). Vitamin D is required, especially for those who get little sun and don't drink milk (think Canada in winter).
She prescribed quinine, to be used only as needed for more severe cramps, since it does have side effects (see post about ear trouble, above, but there are other side effects as well. I see that the Mayo Clinic lists two other possible nostrums.

When I was living in the desert southwest and spending some time in Mexico, and was younger and more active, I took salt tablets or otherwise increased salt intake.
Salt and sliced lime is often served with beer (as well as being part of margaritas). Pizza and other fast foods in Mexico often have too much salt for our taste. Now the doctor recommends low salt intake for me (somewhat elevated bp).
Even here in western Canada, better bars (pubs) serve lime and salt with Mexican beers, it has become trendy to do so.