How do I paint medium colored wood paneling?

You can paint right over it. Make sure you clean the walls really well and then use primer and paint made for whatever material the paneling is made of

You may need to wood putty and sand before priming and painting if there are holes from hanging things. You want it as smooth as possible because once you paint you will see every flaw in the paneling that you never noticed before.

Clean with TSP, prime with original Kilz, then paint with a good paint - probably 2 coats. My daughter's room had 2 walls of paneling that I painted when she was little and it has held up beautifully.