I try to oil my cutting boards every couple weeks - but your time between oilings will vary with how often you use them and wash them. It's dead easy so you really have no excuse to not do it - an oiled cutting board with last much longer than one that's hurting for moisture. :D
Step 1: What you'll need:
- any dry cutting board (it should look dull, the color should be lighter than normal)
- cutting board oil (I use mineral oil)
- a clean rag
Step 2: How to oil the cutting board
Wipe the surface of the cutting board, rubbing gently to get the oil everywhere. You will continue to add more oil and rub until the entire surface of the board is glossy and will take in no extra oil. Make sure to get the sides of the cutting board as well!
Make sure to add the oil little by little so that it gets a chance to sink in to the wood.
Now turn the board over the do the back in the same way.