For your fretboard, particularly for porous woods like rosewood and ebony...
1. Pull off your strings
2. Lightly (eh, somewhat generous, but not dripping) oil the wood
3. Give it 30m ( = one good Dream Theater song, or one good thrash album)
4. With a dry rag, clean up all the gunk the oil has loosened
5. Apply *just* enough more oil to lightly coat the wood again
6. Allow another 30m
7. Restring, setup, Win.