Hot compresses several times a day. Can be a tea bag, or not. My daughter was prone to sties for a while. Her eye doctor told her to take a fresh washcloth every morning, and several times throughout the day run it under very warm water and apply to the affected eye for even one minute was good, as long as she did it throughout the day repeatedly.
This method was easier for her than what had been recommended by her regular doctor -hot compresses for 15 to 20 minutes at a time. The shorter method was easy for her to do whenever she had a free minute. She hasn't had a sty come full since then. Anytime she feels one starting she treats it in this way and it's gone before it fully gets there.