1. Never store your knife in it's sheath long term (ie a month or more).Leather absorbs moisture from the surrounding atmosphere and as a result your knife will be a rusty mess if left in a sheath in most (but not all) cases.
2. Maintain a sharp edge for safe use.
3. After use , clean your knife blade with soap and water and dry thoroughly. A little bit of oil, food grade if using on game, will keep your blade free from any chance of rusting.
4. Saddle soap is a great cleaner for your sheath if it gets dirty. After cleaning apply a little mink oil to keep it from drying out.
5. Johnson's paste wax is a great maintainer for wood and micarta handles. A little with every sharpening is always a good idea. Wd40 works well in a pinch for micarta also.