How can I paint over pine paneling from the 1950s in my kitchen & den?

You HAVE to prime the walls first. I would use an oil primer. It goes on the paneling easier than latex. You might have to do two coats but it will help make painting it a lot easier. Then put on your paint. I used latex. I did the paneling in my laundry room almost 20 years ago and it still looks good. It's easy to wipe down, too.

how much origanal 1950's era character still remains in the house? The pine paneling I've got in my 50's fixer has been oiled. I'm afraid to put a light bulb next to it. Try your paint in a hidden area if you can...and see how well it sticks. Prime, paint. Sample both Just a drip will do.

Rub down - Prime - Undercoat - Topcoat.

Agree with Dfm. It is wise to have a little patience before just diving into the project. Go through all the steps, trying it out on a hidden area first, to not only see what the result is, but how it may or not meet with your expectations.

Do you know if the paneling has been oiled?

Prep it with calking on every space between panels, about every 4 ft for most paneling. Paint it with aroma free Kilz paint, then paint any color over the Kilz primer. We sponge painted our OLD paneling, it was warped and the tri shade sponge painting hid it! If I can sponge paint, anyone can! We also added a border at the top near the ceiling. It was lovely.

You can buy a stain to cover the wood to make it a darker color. Go to Homedepot or Lowe's and see what color stains they have. If you want it completely covered, then look for paint with hjgh-gloss finish. You can clean it with a damp rag. Good Luck!