Cleaning the throttle body just involves shooting some throttle body cleaner into the throttle valve opening. Some people say do it with the engine off, others say do it with the engine on.
Use throttle body cleaner instead of carb cleaner because it won't damage the TPS sensor and other TB parts. Gumout and a few others make a specific cleaner for TB's.
I just took off the air filter box assembly to expose the throttle butterfly valve, and sprayed some cleaner into the opening onto the butterfly valve and surrounding area then wiping the area with a clean rag. I didn't need to spray a lot because the valve wasn't very dirty.
I did it with the engine running; I had to operate the throttle manually to open/close the butterfly valve, and to keep it front stalling because I took off the MAF sensor and disconnected a few things. Of course the ECU freaked out and threw some codes because of the disconnected sensors, but I just reset it when I was done and all was fine.
My throttle body was pretty spotless for 50K miles, but I wanted to do it anyway since I already had the can of cleaner sitting in the garage. I didn't need to use a toothbrush either, just a rag here and there.
Some people say to spray a little silicone lubricant onto the TB butterfly valve and surrounding area, however I'm a little reluctant to spray that into the TB and get it in my engine, so I didn't bother.
