Clean your chain
You could take the complicated route: remove the chain and soak it overnight; disassemble and clean each roller with a cotton swab; and then do something involving pipe cleaners and a solvent. Luckily, there's another way. Buy a chain cleaner such as Park Tool's Cyclone Chain Scrubber (£27.99, www.madison.co.uk) and fill it with Finish Line Citrus Degreaser (£12.49 for 495ml, www.madison.co.uk). Attach the device to your chain, turn the crank 15 revolutions, and let the brushes scrub away grime (shown). Remove the chain cleaner and wipe the chain with a rag. No chain cleaner? Spray Finish Line Speed Degreaser (£10.99 for 500ml, www.madison.co.uk) onto the chain, focusing on small sections at a time (it evaporates quickly), and wipe clean with a dry rag. Apply lube when you've finished.
Adjust your brakes
If your brake lever reaches the handlebar before it stops your bike, either your pads are worn or your cables are stretched. Worn pads should be replaced - but that's another story and you want to ride now, and there is something you can do to get by. Turn the barrel adjuster on the brake caliper (where the cable enters the brake) clockwise one click at a time, testing your brakes after each adjustment. If you reach the last click, and still haven't solved the problem, loosen the pinch bolt (where the cable goes into the caliper) and pull a small amount of cable through (shown). Tighten the pinch bolt and repeat the process until you achieve the right amount of tension.
Smooth out shifting
What good is a clean chain if it jumps around and skips gears? Loose cable tension is the likely culprit. With your bike in a repair stand, shift to the smallest cog. Turn the barrel adjuster on the rear derailleur one-half turn clockwise (shown). Then, as you rotate your pedals, shift gear once. If the chain doesn't jump to the next cog, make another half turn. If the chain starts to jump two cogs for every one shift, you went too far. Back it down a half turn. Don't turn the barrel adjuster more than halfway at a time; you may end up with too much tension, which will make your shifting just as bad, or worse, than when you started.