The air pressure in the pressure tank should be two psi below your pump cut-on pressure. Turn the pump off, and drain the water pressure completely down and then check it with a tire gauge, and release air if too high, and air it up with a bicycle pump or portable air tank or compressor if too low.
The pressure switch can be adjusted by turning the adjusting nuts down on the spring-loaded bolts to increase pressure, or up to decrease pressure. If you have only one adjusting post on your switch, it will automatically be set 20 psi apart for cut-on & cut-off. If you have two, the tallest will be for the cut-on pressure.
Check inside the top of the pressure switch cover, and there may be a diagram to tell you.
See if this helps solve the problem.
As Mark said, there can be a whole range of things that can affect a well and pump, but those are the first two things to try.
Good Luck!
Mike