Clean your bike.
Want to extend the life of your ride? Keeping it clean on a consistent basis is a sure-fire way of doing so.
What to do: Use a basic biodegradable cleaner, a sponge, a towel and an old toothbrush to clean everything: the frame, chain, chain rings, cassette, derailleurs, pedals, brakes, and seat. No need to use bucket-loads of water or (especially) strong jets; a gentle rain-like spray or mist will do just fine to rinse away any soap residue. Also, remove the seat post for a thorough clean, and add a small amount of bike grease before reinstalling it. Your local bike shop's mechanic will thank you!
Watch your wheels.
Wheels (rims) hold your tires in place and provide stability and smoothness while riding. Properly tuned and trued wheels (that don’t wobble or rub against the brakes) mean consistent contact between tires and dirt.
What to do: Elevate your bike and spin the wheels; both should move smoothly, without wobbling. A wobbly rim can be adjusted with a spoke wrench - a simple fix with the right tool, or for a bike mechanic. Replace your wheels if denting or other damage is excessive.