Simple answers for wells: increase the pressure switch setting and at the same time increase air pressure in tank to 2 pounds below cut in pressure. For example on a 30 / 50 switch the tank pressure will be 28 pounds. With a variable speed pump which has no pressure switch the setting will be increased. I would suggest in both cases to have a licensed plumber/well man do the job so that the pump does not work too hard and can shut off.
For city water, it could be as simple as adjusting or replacing the pressure reducing valve. Lack of pressure could also be restricted pipes: galvanized pipes that are clogged, a gate valve where the gate has partially dropped, pipe size too small, or a water conditioner that is not working properly and is restricting the water passing through it.
Pump size or older pump with not much life in it.