1. Don't Sharpen it! What I mean is, with high carbon steel knives, you don't always need to remove material to get it back to sharp. Simply strop (I use this) or hone (I use this) the edge after use. This will prolong the life of your knife.
2. Don't store your knife in the sheath. If you use your blade everyday, this isn't much of a worry. The oils from your hands and the patina from the use will help protect it, however, a sheath will tend to hold moisture and when left unattended, it can rust. So when storing your knife, leave it out of the sheath with a light coat of oil. I use this.
3. Add a Patina. There are too many ways to do this but I'll share two ways...ferric chloride (I use this) or boiling white vinegar (I use this). I personally use both methods, but there's no wrong way to do this. In either case, make sure you clean the knife with the same type of degreaser or rubbing alcohol to get even results.