Soak bottles in non-scented bleach for about 15 minutes diluted in hot water. Rinse bottles out really well and get rid of all traces of bleach. Do this no more than a couple hours before bottling or run the risk of germs reintroducing themselves to your bottles.
To kill yeast and help to further protect your mead from microbes, you can add sodium metabisulfite, but I am not sure how much. Probably a very little bit, but I wouldn't do it based on that. The standard practice I believe is simply adding a campden tablet to your brew. Yes sodium metabisulfite can be used to sterilize your bottles in a strong solution, but cleaning bottles is cleaning bottles and that just prevents adding any nasty things to your mead when you bottle it. This will not kill any yeast or other microbes already present in the mead. Bleach is cheap and effective anyways, so that's what I use for all my sanatizing.
Honey is a natural antioxidant, and the alcohol content of your average mead is a deterrent to microbial growth. Couple this with sanitized bottles and siphoning equipment and proper corking, your mead should be quite safe from spoilage.
You can also add something to increase acidity as well to help prevent microbial growth, but that will effect the taste.