Which do you use? American spelling or British spelling? I usually tailor my writing to my audience, so if I'm writing to my Aussie friends, I will write colour, licence, centre, realise, ar$e ; to the Americans, I'll write color, license, center, realize, a$$.

When it doesn't matter, I try to revert back to the British spelling, only because I think that American is a somewhat bastardiSed version of the English language (I can't stand that words like formulas have become official in the language because kids can't remember that the plural form is formulae. Tsktsk!). But honestly, there are some words of which I don't particularly like the British variant - primarily the "-(i)ze" words like realize and analyze.

I suppose that consistency is the key, and I'd get more scowls from an English [Language] teacher for using half American spelling and half British spelling!