How to paint wooden furniture?

It would all depends on the paint you want to use. Some need primers, some like chalk paint you can use straight out of the can.

https://www.youtube.com/watch?v=gNxxjXAI7-Y

I highly recommend using General Finishes Milk Paint, it's a great paint that requires little prep and no finish coat (unless it's a table top or something with a lot of use). Here's my latest post so you can see an example! https://www.hometalk.com/diy/kitchen-dining/kitchen-dining-furniture/distressed-black-sideboard-makeover-37109275?r=2

I have painted lots of furniture. I just make sure the piece is clean and smooth. I like to use at least a semi gloss. Usually just one coat. No finish other than that. . . think about it, if the paints gets scuffed or scratched it is really easier to just give it another coat of paint.

Check out this handy guide to get you started!