Everybody has their own cleaning process, here's mine: When a keg kicks, I open it, rinse out the trub, fill it half way with water and add starsan concentrate. Close and swish. Drain and rinse with clean water. Pressurize and place in storage until I'm ready to use.
On brew day, I'll remove the keg posts with a deep well socket ( I have ball lock kegs) and place them in a dishpan of starsan use for that purpose alone. I'll rinse the keg again with starsan. I run a dip tube brush through the dip tubes, apply keg lube to all the rubber seals and reassemble, ensuring all the poppets and springs are in place ( A missing spring won't be found until you go to tap the keg: ask me how I know this). I reassemble, fill, pressurize, tag and place into storage until there's a conditioning slot available in the kegerator. One time I have also cleaned the beer lines by taking a half full keg of starsan from my rinsing operation and running it through the tap utill the "beer" in the lines turns clear.
You should have on hand:
spare o rings including those for the poppets, post bases, dip tubes and lid.
Also, several spare poppet springs.