Personally I boil about 3-4 gallons of water, and place the recommended amount of PBW (homemade - one 3lb container of oxiclean free and 1 bag of Red Devil TSP from Ace hardware) into my cornies, add water, and top off with hot tap water.
Soak overnight. In the morning the water is still pretty warm, about 85°-90°f I toss all the posts, o-rings, dip tubes and such in as well. In the morning, I scrub with a carboy/corny brush, and rinse, rinse, rinse, the hotter the water the better. I turn it upside down, let it dry during the day while I'm at work, and lube, sanitize, and reassemble when I get home.
Charge with 30psi to seal and I'm ready to fill next time I need it. I just spray the posts down with some sanitizer beforehand.