It’s easy to take care of a pair of rubber boots - hose off mud and dirt with clean water. Dampen hard, dried mud and let the water soften the dirt for a few minutes before finishing the job with a thorough rinsing. Avoid storing rubber boots in sunshine to prolong the life of the rubber.
Leather work boots can be washed the same way, but take care to dry them well away from sunshine or any heat source. Drying too quickly will crack or distort leather. Occasionally, apply leather conditioner followed by saddle soap, to clean boots and help keep them supple. Alternatively, apply spray-on waterproofing, following label directions.
Dress boots, which usually won’t face such hard use, can be spot cleaned with a water-moistened cloth. Treat these the same way as you would fine shoes. Clean suede regularly with a nylon or brass brush sold by shoe stores for this purpose.
Reference:
Jeff Bredenberg, editor, in Clean It Fast, Clean It Right: The Ultimate Guide to Making Everything You Own Sparkle & Shine.