If you are going to carry it, I would just wipe it down daily with a silicone rag and keep the pivot points oiled with one drop of a good oil. For storage, I would coat the blade with a layer of oil/grease.
It really depends upon how much stainless is in the blade. Most of my Case XX knives rust very easily, which is why I recommended every day. The bolsters also tend to rust, and should be wiped down as well. You will probably just have to keep an eye on it and see how it does.
For my cold steel gunsite, I clean the pocket lint out with a blast of air, and wipe the hard to reach areas down with 50/50 isopropanol/water wipe that I get from work. If I cut something that leaves a residue, I clean the blade as soon as I can.
For supplies you should buy, a good sharpening stone and honing oil. There are many types, you just need to see what works best for you.
Never let your girlfriend use it unsupervised. I made that mistake once and ended up with a broken tip caused by a failed attempt to use it as a screwdriver. LOL And I certainly understand that there are lots of women that would know better, but I no longer take the chance.
A little more info, I live in a particularly dry climate. It rains little. But the knife will get wet periodically I'm sure. It's listed as 6318 Stainless Steel. Since I will be carrying it everyday, is there anything I need to do besides keeping it clean and wiping it off? Is there anything particularly harmful to Amber Bone and do you need to upkeep it? I will also probably use it for food, so does that make a difference?
The area to aim for is the tang of the blade, where the backspring has constant contact with the tang during opening and closing. For best results, open the blade (or blades) perpendicular to the handle and apply the lube directly to the tang. Cycle the blade a few times to work the lube in. For consistent smooth operation, repeated applications at regular intervals will help your folding knife function properly.
I think adding lube every day is over kill. just keep an eye on it. When you notice it doesn't open as smooth, clean her out and add a drop of lube. I haven't added any lube to my cold steel in over a year. She still opens nice and smooth as long as I keep the pocket lint out.
As for brands, just look at some of the popular brands such as Gerber, spyderco or cold steel to name a few. They make a long list of knives to fall into most price ranges.
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I know now I've probably deep-sixed more than a few developing friendships because of misinterpreting that.