On the Civic take off the air cleaner and spray the throttle plate. I try to do this once a year or two years max. After a few mins open the butterfly valve by hand and use a toothbrush sprayed with TB cleaner and give it a scrub. Then wipe off with paper towel.
I tried to clean the TB on the Caravan a while ago. Used the very long spray that comes with the Seafoam deep creep to try and get the throttle plate wet.
Only car I've ever cleaned the throttle body on was an '88 Ford Escort that was TBI. I always just used carb cleaner. The throat was always clean but there would usually be some dark varnish up high where the injector would spray a very small amount of gas. I never could tell any difference after cleaning but, it did make it look better when I pulled the breather cap off to replace the air filter. I'd also spray the fuel linkages to keep the grease and grime off of them.
It was gunked up on my Explorer when I got it, so I removed it from the intake manifold and cleaned it with throttle body cleaner and a nylon bristle brush and paper towels. I replaced the gasket with a new Felpro one.
I do it every oil change, spray it down good and wipe with a towel. Today's cars are very sensitive to throttle body cleanliness....several GM cars will actually go into reduced power mode due to a dirty/gummed up throttle body due to the way PVC systems are designed now a days. The throttle body position sensor must match the pedal position sensor or a code will be set and (if off enough) reduced power will happen. I can't see any car going more than 40-50k miles and not have some sort of buildup on the TB that can benefit from a quick clean.
On my 1988 Escort it's extremely simple so i do it often, maybe 2 or 3 times a year.
I just spray the hell out of it with Brake cleaner.
It always seems to idle smoother.
The first time i cleaned it it was very gunked up, the idle jumped from 800rpm to 1100rpm and had to adjust it back down.
I picked up my Tundra with 73k on the clock, and at 110 or 120k it developed a wonky idle. It was about due for plugs (so it must have been 110k) so I did them and wiped down the throttle valve. Not sure which was the problem. So far, that's been the only car I've "had" to do that on. Not sure if it's from mostly highway travel and usage of good oils or what, but I just haven't had a problem and as such, don't consider it PM (I guess if I changed vehicles I might wind up with something that needs it).
I did some reading and it sounded like it was best to use a proper cleaner for the job, so I got some... from Walmart. It was only later that I read that you might damage something from moving the flap around, and you might need to do a relearn on the throttle position... neither of which I gave any consideration to. Truck didn't care. YMMV.
Nothing on the 12 Camry. I did the Matrix tbody along with the maf sensor and the CRC cleaning kit a few years ago. Then last year had the mechanic remove it while taking care of some other things. He sprayed it down liberally with 3M throttle body cleaner and afterward it looked new again .
The only vehicle I ever had to clean the TB on was my '05 Colorado with the 3.5 liter I5. The CEL came on at about 90k and again at about 180k for "idle speed too low". I removed the TB, sprayed with induction cleaner, scrubbed with a toothbrush, and wiped with a paper towel.