This website is very good at finding out what is in your food choices:

http://nutritiondata.self.com/

Pay attention to serving size...too.

11mg of magnesium is just a bit above an egg which is 8mg

high magnesium foods are beans, nuts, oatmeal, yogurt.
270mg in 3 ounces of almonds for example.

Too much caffeine, alcohol will deplete magnesium.
I wouldn't go whole hog on the sodium restriction. There are reports now and then that sodium is not such a bad thing after all.
Like this:
http://www.cbsnews.com/8301-504763_1...-health-study/

There are many similar articles like this on Google now.

Don't be silly and eat excessive salt, like some restaurants put in their food. But limiting it severely is not necessary either.