Nick -

Some guys use renwax, I keep a light coat of oil on the blade at all times(whatever type of oil I have on hand).

Don't store your knife in the sheath, if it is sitting in a safe or being "stored", keep them seperate if possable.

If your 18 spends lots of time in a sheath on your LBE, pull it out as as often as you can and coat the blade with some sort oil...if your sheath gets wet, make sure you let it dry before putting your knife back in it.

Hope this helps,
Rob