Get Regular Trims
This might sound counterintuitive, but you need to keep up with haircuts, even when you have long hair. It's not true that regular trims will make your hair grow faster (how did that one get started, anyway?), but they will help your hair look healthier.
Long hair more easily looks damaged than shorter hair does, so you should get those split ends snipped every two to three months. Not so much that you compromise your beautiful, flowing locks, of course, but just enough to spruce things up. Strengthening shampoo and a once-a-week deep conditioning will also keep those pesky ends looking perky.