Cold kegs are not a must, but make pouring so much easier. Use plastic keg tubs to keep the kegs on ice.
Lower pressure is sometimes needed because the kegs have recently been jostled. This is especially the case if you are relying on the coils to cool the beer.
Store it clean and dry. Remove the faucets after cleaning and blow out with CO2 to get as much water out as possible. Storing with StarSan in the lines and faucets closed is good as well, but you will want to replace the StarSan from time to time.
Be sure your manifold has check valves if you plan on pouring beers from other brewers. I have seen plenty of backflow due to high pressure kegs. Bleeding the PRV is good before connecting a keg, but it's easy to forget.
Use thick walled line. I like the thin wall for my kegerator, but jockey boxes get moved an abused so much that I have seen the line split at the barb connections.