"As a general rule, is it a good idea to lean your engine during taxi?" - Reno
“Yes, this is a good way to keep your spark plugs from fouling. It’s particularly important to do this if operating an older engine designed for 80 octane, which now uses 100LL with associated lead fouling issues.
Important: If you’re going to lean while taxiing, be sure your “before takeoff” checklist calls for richening the mixture prior to takeoff and be sure to use it!
Don’t worry about leaning too much during taxi. You can’t do any damage other than to your ego if the engine quits on the taxiway.
For example, on a Cessna single you can pull the mixture back about two inches without the engine quitting.”