Cleaning your bike after a muddy adventure can easily be more fun than a chore. Instead of making a dash for the shower when you get home, roll up your sleeves and first attend to your steed's personal hygiene. It makes sense to rip into it while you're still hot 'n' grimy and before corrosion can attack your expensive components - a stitch in time and all that. It's also a good bonding session for you and your bike. You'll discover new things about each other - worn parts, sore bits, unloved bits... and then there's the bike.
Water is your bike's best friend and worst enemy. Use just enough to wash off the bulk of the offending muck without swamping the hubs, gears, brakes or other vital parts. A steam cleaner or high pressure hose makes quick work of it but you risk stripping protective grease and lube or worse, forcing water into erstwhile smooth running bearings. That's okay if you're a pro racer with a mechanic to strip and rebuild your bike... but back on planet earth. It's generally necessary to whip your wheels off so you can do a thorough job. A good rub with a soft brush and a little detergent is next. Beware of weld holes and other entry points where water may find its way into your frame. If you hear water sloshing around then you've sprung a leak. Take out your seat-post and hang the bike upside down for the night with the bats in the attic.
Now rinse and dry off with a soft rag. This is a good time to lovingly fondle your bike and check for any broken or loose bits. Your chain is easy to keep clean and lubed - point your mouse at 'Chain care' under 'Maintenance' in Tech Tips. Keep your brakes and braking surfaces clean - you minimise wear, avoid unfriendly screeching ... and they just work better. All moving parts (brakes, gear shifters, derailleurs etc.) should be sparkling clean and lubed with grease or oil as appropriate. Try some silicon spray - it magically penetrates and lubes in one. CRC gives immediate relief but doesn't last and eats into the residual lube you want to preserve.
Gear cables get gunged up with a combination of mud, rust and water. You know this procedure is overdue when changing down becomes 'sticky'. They are easy to clean. The trick to releasing your rear derailleur cable is to put your bike in a stand or hang it by the seat with an old tyre. Select the hardest gear at the back (smallest cog) and then while still pedalling, manually ease the derailleur over to the biggest cog. The cable goes all floppy letting you release it from the stops and shuffle the housing backwards and forwards letting you clean and lube the entire length. Deploy the same general idea to sort your front derailleur.
Suspension booties, fully enclosed cables, internal hub gears, disc brakes, derailleur boots... oiling your frame even. These can all help to repel dirt and water and lessen the amount of TLC required to keep your bundle of joy purring.
When summer starts poking its head around the corner and the trails begin to dry out, it becomes worthwhile to consider shouting your bike a spring overhaul. Those annoying clicks and squeaks take on real meaning when you can actually see which part of your bike is trying to communicate with you. Get it looking clean and pretty, then wheel it down to your local bike shop for a full service - mechanics generally respect that 'one careful owner' look. Consider replacing all of your cables (you can probably skip the front derailleur if you are running low on cash), brake pads and chain. Depending on the amount of wear, you can probably fit two new chains before having to splash out on a new cluster and chain rings. They'll also check out your shocks, headset and have a good hunt around for any other areas requiring remedial work. There are heaps of things you can do yourself too - pull off your tyres and clear out any water or mud that's shimmied its way in. While they are off, lightly buff your rims with a steelo-pad to remove any break-pad residue. And hey presto, a nearly new bike, that shifts, brakes and performs like a new one ready for some full on summer riding.