What oil ?
I use sweet almond oil, with added vitamin E (get in a pharmacy) Synthetic oils are generally not recommended.
When to oil ?
As often as once a week in the beginning ; afterwards, about once a month (again, if you know who made your flute, ask the maker directly about oiling it).
How to oil ?
Oil the inside of the bore and leave to rest overnight; in the morning wipe off the excess.
You can also lightly oil the exterior of the instrument.
2 Cork Grease
Grease the joints each time you assemble the flute. This will protect them and prevent the cork from swelling or drying. You can also apply grease to the tuning slide if needed.
After playing, wipe out the excess humidity with a cloth on a cleaning rod. Use plastic, not metal cleaning rods to avoid scratching the wood.
4 Play !
Every day !
If you play your flute regularly, the sound will improve with age. An unplayed flute can dry out or even crack.
When you are not playing, store your flute protected in its case
5 Some Problems
I can’t disassemble my flute.
The joints have swollen : never use force, leave the flute some time and try again.
The joints are loose.
This can be quite common with wooden flutes. You can re-tighten the joint with a couple of turns of thread or teflon tape.
My flute doesn’t sound right
Always warm your instrument up before playing : a half hour is good.
If you haven’t played your flute recently, the sound may have deteriorated. It should return to normal once you start playing again.