I soak mine with an oxyclean/water solution for a day with the ball lock liquid connector, hose, and tap in the keg. Rinse it all really well and then fill it about half way with sanitizer. Then I hook the keg up to co2 to pressurize it and push some sanitizer solution through the line and tap.
After that I normally have a freshly carb'd keg already in the fridge waiting for my line and tap to be hooked up to it and I let the keg with sanitizer sit in it for a few days/weeks until the next brew is ready!