Post Run Cleaning

I usually hit the self serve car wash on my way home and give it a full spray down just on the water setting to get all of the muck out from under the fenders and anywhere it would want to rust. The engine bay I do less frequently but usually do a full soap down when I do. There are things you can mess up under your hood if you use too much pressure or aren't careful, so mostly just keep an eye on what you're spraying and make sure nothing comes loose and try not to get too close to electronics/fuse box or other places where water could get trapped and rust. Radiator should be totally fine to give a full spray down and probably something you want to do as mud stuck in the fins will reduce air flow and proper cooling.

Beyond that I mostly just fix things when they break and check fluids occasionally to make sure everything is topped up!

Avoid directly spraying the alternator and spark plugs, they can get wet but you dont want water getting trapped in them. If I'm doing a full clean I'll take battery out and wrap up the alternator with a plastic bag, but for just a quick spray down I usually just wait till next morning so the engine is cool, start it up and spray it with water. That way if water does get into alternator, it'll dry out with the engine running.

Yup, what Nick and Shane said. Mine is covered in dirt but was banking on the rain. I like to take the mats out and give those a power wash too and get in the door jams as well.

In terms of being ready, you can always keep a container of some essentials like oil, coolant, basic tools, straps, blankets, canned food, never know when you may need those things are always good to have on hand.

What all those guys said and one tip about spraying rads, coolers and condensers (because they do a great job of holding mud, grass, seeds, etc.. lol)
if you are use a pressure washer ( some are more powerful then others, use caution) always hit the fins straight on and don’t hold it too close. Otherwise you will be sitting in front of the rad for a while with a pick restraightening all the fins that run in between the tubes to dissipate the heat. And if they are stubborn and fairly accessible in the vehicle then a garden hose to get a good volume of water soaking from the inside to help back flush the gunk out the opposite way it got jammed in. Also spray nine or something like it works well to soften stuff up too.
And the suds make it look like you are doing something. Haha. When in doubt shine a flashlight through it and see if light comes out the other side. It’s good clue other then a good steady strip of clean water.
And finally if it’s really bad you just suck it up and pull the rads out to really get them clean.
Sorry guys. That was waay shorter in my head then writing it all down!
Cheers!