Bikes are a great way to get around - they're fun, they're cheap to fuel (they burn only calories) and they're a great way to get fit. After a day spent tearing up and down the hills - or even over a dirt track - bikes can end up very dirty very quickly.
You do have to clean your mountain bike same as doing the house cleaning, even though you are going to take it out again next weekend and get it completely covered with mud all over again. Leaving your bike all muddy can cause parts to wear out more quickly, and dirt and grit do your chain and gears no good at all. Besides, mud can even cake up your brakes, meaning that they don't work as well as they should to ensure your safety.
It's best to clean off your bike as soon as you can after returning from your outing - after you've seen to any bumps and bruises that you've collected and had a bit to eat to top up your energy levels. This is one advantage that bikes have over horses: they're not going to stand there hungry, whinnying and cold waiting for you to have a shower once you get back; nor do you have to see to their needs while you're hungry, tired and cold - or bleeding. You can even leave it until the next morning, if you like.
First of all, use a hose to get rid of the worst bits of dirt and mud. This is where acting quickly really helps - if the mud is still wet and fresh, it comes off with the hose and no scrubbing is needed. If the dirt has dried on, a soft scrubbing brush may be needed to take stubborn cakes of dirt off. If you really want to make your bike gleam, then use warm soapy water or any other house cleaning product, as you would do with a car.
Pay particular attention to the chain, the brakes and gears. Check that no dirt and/or stones have managed to get in to the mechanisms.
Once you have made sure that all the dirt is washed away, check over the paintwork of your bike very thoroughly and check that no chips or cracks have been made in the paint. If the metal tubing below the paint has become exposed, then touch this up with a dab of enamel paint, using a very fine brush. You should be able to find the shade of paint you need for your bike at a model shop. It's wise to buy some before you need it Apply the paint to dry metal and let the bike sit for a day or so after touching up the paint to allow it to cure properly.
After checking the paintwork, you may need to re-lubricate the chain and the gears to make sure that they can run smoothly. Also check the brakes and tighten them if this is needed.
You may also want to clean the tyres, especially if you have been riding over terrain that may cause punctures, such as sharp stones, spines - or even broken glass. Deep tread picks up a lot of dirt, but you won't be able to make the most of the added traction of deep tread if it's clogged up with muck. Use a scrubbing brush or even the tip of something smooth and hard (like a hoof pick, a nail file or even an old blunt knife) to scrape out stones, mud, grass, etc. from the tread. This step will make you much more popular if you have to park your bike somewhere indoors, as you won't bring as much muck inside.
You could, of course, black the tyres and polish the chrome if you want to. But for the mountain bike enthusiast, this is unnecessary. Bikes are for riding and having fun on, not showing off the paintwork!