The "deep litter method" was one of the most important poultry developments of the Twentieth Century. It resulted in a dramatic drop in disease and a reduction in the amount of labor it took to keep a flock of chickens. It also gave an early example of how biodiversity works to our advantage, even with confined livestock.
People these days think they know what "deep litter" is, but mostly they don't. Here's a quick checklist:
Deep litter is not about compost. It's about healthier chickens. Do your serious composting on a compost pile.
More is better. It's not deep litter unless it's at least six inches deep.
Compost as a clean-up tool.If the top of the litter gets caked over with manure, skim off the caked part and toss it into a corner. Within a few days, natural composting will cause
it to turn back into litter again.
Litter is a probiotic. Deep litter has anti-coccidiosis properties (it develops a population of microbes that eat coccidia), but only after it's been around for a few months, so never remove it all. When you start bumping your head on the rafters, remove part of it, but not all.
Lime helps. Stirring in hydrated lime at about ten pounds per hundred square feet will keep the litter more friable.
Chickens don't wear gas masks. If you can smell ammonia in the chicken house, you don't have enough ventilation. Open the windows, even if it's twenty below outside. Ammonia is a poison gas; cold weather is just a nuisance to grown chickens.
Don't break a sweat. If you're spending a significant amount of time messing with the litter, you're doing it wrong.