I've found having environmental switches helps more: I try to use British spellings at home, and US spellings at work, and thus have to constantly think about them. I have spell checking dictionaries set up appropriately in both environments, so I get nice little reminders "you're not spelling it right!" to wake me up, too :)

Because I can't settle in to a routine pattern, it keeps me significantly more aware than previous "develop a new replacement habit" changes have for me.