to clean the bike. Hose the bike (ordinary garden hose is fine), spray with Muc-Off & allow it to sit for a few minutes. Do not let it dry. Hose bike off with light spray pressure, using a brush (a clean paintbrush is really good) to get rid of any tougher stuff.
If you're taking the chain off to clean thoroughly, soak it in kerosene. It can help if you place the container on a washing machine (if it's in use!) or similar, so the vibrations can shake the gunk out of the chain to settle in the bottom. You may need to give it a couple of goes to really get it clean. Once it's clean, wash the kero out in warm soapy water, then rinse the water out by swilling the chain in a container of methylated spirit. Allow chain to dry (metho will mix with the water in the chain, and draw it out as it evaporates). Refit chain then lube. Your choice of lube depends on the conditions you ride in. Dry wax or Teflon lubes are good in dry weather, but soon wash off if it's wet. Wet lubes are more tolerant of wet weather because they form a barrier on the chain, but more frequent cleaning is required to prevent dirt build-up.
Many people here (myself included) use ProLink, which is a wet lube, reasonably wet-weather tolerant, although not quite as good as some, but doesn't get sticky, so it doesn't attract the dirt as much. It's a good compromise between the clean dry lubes and the water-resistant wet lubes.
NOTE: The shop I work in sells both Muc-Off and ProLink. I personally choose both over other similar products we stock..