How To Paint Over Antique Pine Furniture?

Don't know where you live, but if you live in the United States, the furniture is antique and you paint over it, then it will lower the value of the furniture by around 75%.
  To answer your question; It would depend on if the furniture has polyurethane over it or not.
If it doesn't, then you can just use a good paint made for painting wood, but if it has a clear coat finish on it, you will need to prime it with a primer made for slick, non porous surfaces, let it cure for a few days and then paint.
  Would be a good idea to talk to your local paint supplier about which primer and paint to use.
It is very difficult to advise on paint procedure without knowing anything about the finish on the pine.