1. Never Let Your Tread Wear Out: Replace your tires frequently. With fresher rubber, you'll have fewer flats and also a better-handling bike.
2. Regularly Inspect Your Tires: Sometimes you'll come back from a ride with small bits of glass or debris embedded in the outer casing. If you habitually clean this stuff off, it won't have a chance to work through the tire.
3. Same Goes for Your Chain: Keep it clean and lubed and your bike will shift, and look, better. I use T-9 bike lube [4 oz, $8; boeshield.com] for dry weather and Tri-Flow Superior [2 oz, $5; triflowlubricants.com] in wet conditions. And if you replace your chain before it gets too worn out, you'll save the expense of having to fix or replace pricier items like cassettes and chainrings, which suffer increased wear and tear from old chains.
4. Buy a Torque Wrench: I have one from Syntace [from $166; syntace.com] that's very cool. Modern bike components are made of expensive materials like carbon and titanium and highly engineered to save weight. But that also means they can be damaged by overtightening. Manufacturers test their products and provide torque recommendations. Make sure you follow them.
5. Find a Good Local Bike Shop and Mechanic, and Be Loyal: The more familiar they become with your bike and your riding style, the more able they'll be to keep everything working to your liking.