I prefer it plain when used on a Reuben sandwich, & sometimes with a sprinkle of caraway seed when used as an accompaniment over Czech Bread Dumplings with Roast Goose.
When I've used kraut as a side dish, I normally serve it as is (somewhat drained), or if it's a bit to zippy, I'll saute it for a few minutes with a pat of unsalted butter, then serve.