I do what QuiltE says but usually celery is not something I worry so much about, plus I just have the freezer attached to my refrigerator so not enough space to put up a lot of foods.
You can put them in baggies with a small amount of water, but easier to just do them dry so they can right into whatever you are cooking without having to drain.
Finely minced celery can be added to a lot of things, I like it in my spaghetti sauce. Just throw it in with the garlic and onions and stuff like that, or if you are browning meat you can put it in that step too.