I sharpen them by hand and by eye. To put an edge on a knife I use a stone starting with a fairly coarse one. I lay the stone on my bench and work the knife two strokes on each side back and forth, careful to keep the angle consistant. To get the correct angle, hold the edge at 90 degrees to the stone (straight up and down) and rotate the blade to half that angle, (45 degrees). Half that angle again by eye and that's the angle of approach you want. Use a finger on the dull side as a reference to keep the angle consistant.
Once it gets sharp I switch to a very smooth polishing stone and work it as above but lightly and even more carefully. If you look at the edge after sharpening with the coarser stone with a magnifying glass, you'll see that although sharp, there's wee little bits of burr on the edge. A lot of guys make the mistake of not getting rid of these microscopic burrs. That's where the polishing stone comes in. Carefully finish it off so that you can't see any burs with your magnifying glass. Now, you've got a sharp knife. And the edge will last unlike if you don't deburr it. (800 grit or so good quality sanding paper will work if you don't have a polishing stone).
Other than that I use a big steel usually to touch it up now and then, or a tiny eze lap pen sized thingy that I just bought to touch things up in the field. I find though that any knife that's used a lot needs the thourough going over every once in a while starting with a coarse stone, carefully deburring it. I've finally got to where i like sharpening knives. Got in to it more by trying to keep good quality wood chisels doing what they're supposed to do.
