Check your air EVERY RIDE. If you don't know your pressure, ask a coach. The proper tire pressure depends on several factors:
Rider weight
Lighter rider == LOWER pressure
Heavier rider == HIGHER pressure
Tire size
Bigger tire (2.4, 2.6.) LOWER pressure
Smaller tires. (2.1, 2.2, 2.24, 2.3, 2.35) HIGHER pressure
Tubeless/tubed (if you're still running tubes, stop it)
Tubeless == LOWER pressure
Tubes == STOP IT (also HIGHER pressure)
Rider style
Smooth. Lifts all obstacles, finds landers. LOWER pressure
Gorilla. Slams into obstacles. HIGHER pressure
Clean your bike. Do a good job, here's how:
Rinse the bike with a hose. DO NOT rise the bike with a high-pressure washer. Just don't do it.
Wash the frame, tires, wheels, brakes, pedals, chain, cassette, front ring.
DO NOT spray into any bearing races. Basically, don't come at the bike 'horizontally' with water - spray from the top down.
Dry the bike. If you have a compressor blow the water off the frame but be careful to not blow air past any seals (fork, headset, etc.)
Wipe the frame down.
Dry the brakes only with compressed air, do not touch brake pads or rotors.
Lube the drivetrain
Use a bicycle specific lube. You can also wax your chain for an extremely clean, low maintenance drivetrain.
See the Accessories Accessories page.
Check cockpit, stem bolts are tight. Don't overtighten - use a torque wrench
If your bike isn't shifting/running correctly take it to a mechanic.