Every two or three years, usually at the beginning of a summer, I get a haircut. About 15 inches get trimmed off, and most of it goes to Locks of Love - a charity that makes wigs for children with cancer or other hair-losing medical conditions.
After that, I do nothing. I wash it, I brush it when it gets long enough to need it, I use cheap ponytail holders. Otherwise I go about my business until it's time to do it again.