Our tub/shower has a spout and 3 knobs (hot/cold/shower). When I turn on water, then turn shower knob, there shower works, but pressure could be better. Also, the tub spout continues to discharge a lot of water. I know it is a diverer problem, but what is need to fix problem, and how do I do it?

Remove the diverter stem and replace the washer... should resolve the issue!

Mark

You are correct, It is a diverter problem Leaving the hot and cold shut off remove the handle and diverter stem, (see image) Replace the washers and then check the seats fro nicks or rough spots. If the seats are OK the reassemble and test.
However, if the seats are damaged they must either be replaced or if that can't be don the valve will have to re replaced. Let me know what you find. Good luck, Tom