[Ed in SoDak]

If you're getting many stations at one point on the dial or crowded together, it's more a receiver limitation than anything you can do by tweaking things. Best avoid twiddling coils and such inside the set unless you have a good service manual and tons of patience.

For good, wideband sound, tuning on "hi-fi" receivers is necessarily broadband. This can let in several stations at once. Didn't used to be so many stations out there, I guess. You can add a preselector, or antenna tuner, which is a simple circuit to build or pretty cheap to buy.

Might just be some sloppiness in the tuning due to age of the dial cord. Rub the dial cord lightly with soft wax such as beeswax, incidentally, that's used to coat old capacitors. Modern candle wax might be too stiff.

For my AM listening, I discovered a big improvement just by running a very long wire outdoors, mine's over 100'.

Ideally, for sharper tuning, you may want to look into a set specifically designed for DX listening. If none of the above seems to fit, it may be some part or other has moved beyond spec and your radio's not performing as it should.

Good luck!