A: First off, if your pickups sound great, leave them alone. Some players swear that removing the covers from humbuckers makes them sound better, but if that was indeed the case, pickup designers like Seth Lover (who designed Gibson’s first humbucking pickup) would never have put covers on to begin with. Still, it’s a personal choice and players like Jeff Beck and Jimmy Page have removed the nickel covers from their humbuckers.
Potting is a different matter. If your pickups (humbuckers or single coils) squeal, shriek and make a loud (and annoying) whistling noise that sounds a lot like a cheap mic feeding back, or if you touch the metal cover on a humbucker and hear a loud bang or pop, you might want to consider having the pickups potted. There are two methods of potting: One is with wax (either paraffin or beeswax) and the other is with epoxy. If you use epoxy, keep in mind that you’ll never be able to remove it in the event the pickup needs a repair. If you have a vintage guitar from the 1950s or ’60s (or possibly even later) you should leave the pickups alone, as potting them now would likely devalue the instrument. A quick caveat: If a pickup sounds bad, potting will not make it sound better. Replacing it with a newer (and possibly better) pickup makes more sense, as pickups aren’t terribly expensive. Finally, have a qualified tech do the potting. It’s more difficult than it sounds and an improperly potted pickup will often need to be replaced.