These three simple tips will keep your AR running like the mailman. Neither rain, nor sleet, nor dust, nor Arctic cold will keep it from going bang when you pull the trigger.
Oil It Up
A generous amount of oil on the bolt and bolt carrier group is the best way to keep your AR in action. Any oil built for high heat with moderate viscosity will work, including synthetic 20W50 motor oil.
Inspect Your Mags
A faulty magazine will bring any AR to a grinding halt. Test different magazines in your rifle and mark the ones that work well. Periodically disassemble and clean the magazines to keep them free of dust and grime. Toss any that don't work well.
Blast Your Trigger
Every round you send downrange with a gas-operated AR blows dirt and gunk into the receiver, some of which accumulates on the trigger. Spray down the trigger group with a good blast of brake-cleaning fluid to keep deposits from building up.