Spinach comes in bags now, so no need to bother with buying a bunch and cleaning it, but, hey, if you want to, go for it!
Me? I buy a big bag of pre-washed, put it in the collander and wash it again, just for kicks.
Then, I melt about 1/2 a stick of butter (not margarine, I never use margarine - ever!) over low heat. When melted, I sprinkle a bit of sea salt, perhaps a teaspoon, and a bit of fresh ground pepper over the butter,and add about 1/4 cup of cheap red wine. (You can use expensive, but it makes no difference).
Pour the spinach (alll of it) into this, and stir it around until the spinach is reduced, but not limp.
HMMMM, HMMM, Good!