"As a general rule, is it a good idea to lean your engine during taxi?" — Reno R.
“Yes, this is a good way to keep your spark plugs from fouling.
Don’t worry about leaning too much during taxi. At low power settings you can’t do any damage with the mixture control, other than to your ego if the engine quits on the taxiway. On a Cessna single you can generally pull the mixture back a full two inches without the engine quitting.
However, you can damage the engine by taking off with a too-lean mixture, so it’s important to enrichen it before takeoff. Be sure your before takeoff checklist calls for setting mixture prior to takeoff, and be sure to use it!
Here’s a way to safeguard against forgetting: Set the mixture so lean that’s there’s just enough fuel to keep the engine running at taxi settings. If you try to add full takeoff power, the engine will stumble and possibly quit. It will be obvious what you forgot. You might damage your ego, but the engine will be fine.”