I keep thinking of notes to add – sorry.
Whether using diamond or regular stones, keep them watered (except oil stones). The slurry it creates assists with honing. If you hone the blade dry, the metal shavings will build up and reduce its effectiveness. This may be the case with the field sharpeners if you don’t have water nearby, so I usually wipe the stone on my pants leg every few passes to remove the micro-shavings. You will feel the difference in the bite as you push the blade across it.
As for learning proper angles, it just takes practice – but you need to be mindful of the grind angle for the type of knife. For example, a Scandinavian grind is an 18 degree inclusive angle (9 degrees each side of the edge). Kitchen knives are about 10 degrees per side, and standard factory edges are deeper at about 20 degrees. Best bet is to use a cheap WalMart knife to practice on until you get the hang of it. You’ll know by feel and sound if you inadvertently shift your angle and eventually will imprint the muscle memory to get consistency.
Just as with drilling technique, it’s a good idea to train your offhand to sharpen so you can push the blade away from you as you do so and avoid accidental cuts. This is especially important if you have to sharpen a longer blade. This really takes practice, so again, use a cheap throw-away for starters. A good way to train both hands, by the way, is to mark the cutting edge with a Sharpie and check your progress with each pass. This will also reveal faults in the factory edge that need correction after you’ve established the skill.
While honing, push the cutting edge against the stone with two hands – one on the handle to guide the blade, the other to apply light pressure to the end of the blade. When stropping, draw with the cutting edge and avoid turning the wrist at the end of the pass – this will convex point while leaving the base of the blade flat. If you want a full convex edge, lay a foam pad under the strop or use a barber’s strop hung from a hook. Otherwise, keep the strop on a solid surface.