Here's what you should use to keep the edge on your knives the keenest:
If they're really dull, you need to spend some time honing them. I really like the diamond stones - they cut fast and they leave a reasonably fine edge.
If you have a knife that doesn't need honing (and if you care for your knives well, they should almost never need honing, except to work out an occasional nick in the blade) keep a good sharpening steel around. These are actually files with very fine teeth along the length of the steel. Also, the action of working the knife over the sharpening steel serves to raise a burr, or what is sometimes referred to as a "wire edge" and it also serves to work-harden the steel at the edge.
If you have a knife that needs an extra sharp edge, stropping is good, especially if you've raised a burr or wire edge, working the blade with the strop will remove the wire edge, but I often will put a spiral sewn soft cotton buffing wheel on an arbor and then charge that up with some rouge and use that on the edge. You will get a blade sharper than a surgeon's scalpel.
Basically, the process is to grind off metal, making the edge as sharp as possible. The more coarse and faster cutting the griding material the rougher the edge you'll have on your knife blade's edge. Switching to finer stones, or a strop or buffing wheel will then use even finer cutting action to get an as-near perfect edge as you could get. But I do like using the steel as the raising of the burr and the action of working the edge over the steel does do some extra hardening of the steel at the blade's edge.