I stopped getting taller around 22. Then again, I never had a growth spurt, so I went from being a tall child to a short middle schooler when everyone else hit the puberty growth spurt, and then slowly but steadily made my way out of the realm of short and into the realm of the taller side of average.
My brother, on the other hand, hit his full adult height of 6'1 at the age of 13 and stopped getting taller then. He got nervous during college that I might catch up to his height, as he was so used to being taller than me.
As for the youngin's trying to maximize their height--really, the best bet is to avoid doing things that can stunt your growth. Don't go on severe calorie restriction (the way many wrestlers or boxers or rowers do to try to make weight), don't smoke (it's stupid to do so anyway), and there's some suggestion that trying to lift too heavy of weights while you're still growing can cause premature growth plate fusion, but that's not entirely settled yet. To be on the safe side, though, you might want to consider more reps of lighter weights if you think there's still a chance of ekeing out another inch in height.