[Scooter2112]

I use boiled Linseed oil just the way that Weldaar states. Rub it in 3-4 frets at a time, so it;s wet, but not soaked. Let it sit for 30 seconds, and rub out any remaining excess. Just did one last night, and it darkens up the wood nicely.

This oil is made to condition and protect wood. To do a whole fretboard takes about a tablespoon. If you play every day, you;ll notice that the smell of it goes away in about a week.