Give the chain a squirt of lube every 300km. Every 1,000 to 1,500km, clean and re-grease the chain, and check chain tension.
Its best to lube the chain after a ride, not before. After a ride the chain is nice and hot so the lube will penetrate into the links more deeply.
Your bikes handbook will detail the correct amount of slack, as well as how and where to measure it.
Adventure, supermoto and trail bikes, with their longer suspension travel, can have more chain slack. But, as a general guide for most street bikes:
- Loosen the rear wheel spindle until it can be moved by hand (on some older bikes you may also have to loosen the bolts on both ends of the rear brake calipers retaining arm)
- Turn the adjuster bolts on each side of the swingarm clockwise by one flat of the bolt head (a turn of one flat on each adjuster is usually enough to take up the excess slack through wear and will maintain wheel alignment)
- Tighten up the spindle nut, then recheck the chain slack (its essential to re-tighten the spindle nut before measuring the tension, as the clamping action affects the tension of the chain)
- Re-check and adjust again if necessary.
Think about the way you ride as this has a big effect on the chain. The harder you accelerate, the more you stretch the chain.