The dilemma: Keep your chain lub'd without attracting too much dirt. The rule for long chain life is never lubricate a dirty chain, as this washes abrasive particles into the rollers. Chains should be cleaned before lub'd. An alternative approach is to change the chain frequently, then proper care is less important, however, the new 10 speed chains are not as cheap as chains used to be.
ZEN: It's a wonderful but imperfect world - Dirt happens and we clean it.
RULE: Chain should be clean before it's lub'd. But don't sweat the details - it's just a chain.
FOCUS: Ride your bike - don't anguish over the equipment too much. The chain will wear out.
Avoid taking the chain off the bike to clean it - this will create more potential trouble and trouble is what you want to avoid. I've heard countless stories from riders who end up with a broken chain after an imperfect reassembly. If you're a chain removal advocate then you're probably a reasonably good mechanic and this rule doesn't apply to you.
Buy a chain cleaner you can run the chain through while it's still on the bike. Park Tools makes one - I use it and it's relatively effective. The Park chain tool will remove enough grit to make the lub job effective. Keep the chain relatively clean and well lub'd for a reasonably quiet ride.
Remember why you have a bicycle. If you bought it to admire the perfection and beauty of its mechanical simplicity then do what you have to do. If you bought it for the benefits and pleasure of riding and staying fit; clean and lube the chain frequently (every 250 miles ). If the chain gets dry, apply a lubricant to reduce the noise. A dry chain doesn't shift smoothly and is noisy.
Replace the chain at least every 2500-3000 miles to avoid cassette replacement. If you run your chain too long you'll have to change the cassette (gears) otherwise the new chain will skip on the old worn gear cogs. If you keep the chain relatively clean the cogs will last longer.
You want the chain and cassette to last as long as you're unwilling to buy replacements. A perfectly clean chain will not last forever - it will stretch and it will break. I've put 15,000 miles on a chain without a mechanical failure but I had to buy a new cassette when I replaced the chain. Also, I was nervous about breaking the chain during the weekly training race. It's easier to keep it relatively clean and replace it every 6 months (if you ride about 500 miles a month).
Some Chain Lubes: