1st and most important rule - don't leave food on your knife. Use it, wash it with warm water and soap, dry it thoroughly and put it away. This procedure is half of the battle. It might be a slight change in your routine but it will become second nature. Carbon steel will patina, as long is doesn't turn into red/orange rust, you're in the clear. If you would like a petroleum-free blade oil for peace of mind I recommend Camellia Oil.

2nd rule - Do not leave wood handles wet. I use naturally oily and dense locally sourced hardwood for my handles to cut down on my carbon footprint but also to use the beautiful resources we have in our own backyards. Natural wood breathes and moves with the introduction of moisture. I seal all my handles with a Japanese liquid glass finish but this will eventually wear off with constant washing. Best practice is to make sure your hands are clean before you use the knife and wash the handle minimally.

3rd and final rule is to use and store your knives responsibly. Only cut on soft cutting boards (wood is really all you should be using) and don't cut dumb stuff. A rule of thumb is that knives with thin geometry are meant for softer ingredients and thicker knives can handle harder use applications. Storage is just as important. Make sure your knives are stores in a cool dry place where the edge cant contact other objects to make them dull. A saya, knife roll or magnet with a leather or wood face works great. That's it!