How often should I clean my bike?
I've used it several times over the summer, but only once in muddy conditions, should I clean it after every ride or once per quarter?
There's a saying that a clean bike is a happy bike. You really can't clean a bike too much.
Make sure to clean the bike more often in the winter when riding on road salt, which is bad for the drivetrain.
For all bikes, I'd definitely clean the drivetrain if it gets muddy. Mud can interfere with shifting and braking.
Do not put oil or grease on the rims. If you have rim brakes, they may squeak after cleaning the rims. As long as it doesn't interfere with braking power, I don't worry about that. The clean-rim-squeal-sound goes away on its own after a bit.
In terms of the frame: With a steel frame, you'll need to worry about rust, particularly where you have any scratches in the paint. Patting the bike dry after a ride in the rain should deal with that.
(This applies to steel and aluminum, I know very little about carbon or Titanium frames, or about disc brakes.)
In my world how often you clean really depends on how convenient it is for you to clean your bike and how much you enjoy a clean bike.
For myself I have a fairly convenient set up so I clean my bike(s), in parts, almost every time I ride. For example:
I go on a ride ('cross ride perhaps) and I come back with a moderately dirty frame and drive train. Knowing it is fall and that if I do a top to bottom job it will only be dirty again tomorrow I simply hang the bike in the stand, turn the hose on it (low pressure working top to bottom, front to back) and remove the majority of the mud etc. Grab a rag, wipe down the chain and re-lubricate. Done. If I ride the same bike the next day, after the hosing I might clean the rims and brake pads or fix the bar tape etc. etc. Each day sees something small being tackled resulting in my actual tune ups taking 10-15 minutes tops.
For my setup that constitutes 3-5 minutes of my life and typically gets done after every ride which gets some sort of road grime on the bike.
I like to operate on the 'clean before anything goes wrong' principle. When you are cleaning your bike you are also inspecting it for wear and tear.
But really, how often do you have to? It all depends on your preference in terms of how you like the bike to operate and how often you ride it (them).
To give some context: I just ride on roads and I cycle for fun and transport. I'm minimizing cleanup-time while trying to maximize ride smoothness and bike(part) lifetime. From that I clean my bike (and by "my bike" I mean "moving parts of my bike" i.e. chain, gears, all the gear-changing stuff, the sides of my rims (where brake-pads hit)) when one of these is true:
Since 3 and 4 are basically "error conditions" I usually try to clean it after either 1 or 2 becomes true. Again, this is only for the moving parts. I clean the rest of my bike when I'm already going to clean it and I'm really annoyed by the amount of dirt sticking to my bike.
Depends on what you want from your bike.
If you're bike is a high performance, lightweight machine and you expect many years of trouble free performance in tough conditions, then wash it as frequently as you can.
If it's a knock-about treadly that you use for the short commute to and from work and for getting your shopping, then wash it as infrequently as you care to.
The only thing that really needs regular cleaning and lubricating is the chain. If you aren't planning on cleaning the chain too often, then ask your bike shop about which chain lubricant will last the longest. You probably want to lubricate the chain at least once a month.