I have a shutoff installed directly below the skimmer and directly before the return - I turn both to off before unscrewing the cap - one of the best things you can do is install shutoffs - if you add them after the fact, and think you'll get a flood trying to get them istalled, plug the skimmer bottom wityh a rag or rubber stopper before disassembly - same goes for return jet - remove directional eyelet and install some type of plug.
Get the larger inline shutoffs that have a quick disconnect on one side so you can easily remove your plumbing when it comes time for winterizing.