Dice the celery and peppers and put in a bowl with the juice of the lemon, stir and add the mayonnaise and the horseradish.
Add the crabmeat and stir.
Add salt and pepper to taste.
Other additional ingredients (not all at the same time) that I've tried and liked: add half a diced cucumber; a teaspoon of capers; dash of cumin, sprinkle of dill, pinch of Old Bay seasoning; whatever you'd like!
Serve on toast, a muffin, in a bed of mixed greens or in pasta.