Headsweats headband, terry thumb gloves, helmet with good airflow (some are better than others). If it's really hot sometimes wear a terry wristband mainly as a "face sponge". Also make sure to have your barber keep those eyebrows tidy! - helps to prevent that thing that happens where all the sweat collects then spontaneously releases all at once into your eyes....usually on a climb. The worst!

Oh yeah another tip I do, once in a while stop and "wring" out your helmet pads by giving a push here and there on helmet with head tipped appropriately.