Respect the medicine. Consider that traditionally medicines that fall to the ground are to be discarded and medicinal herbs should not be placed on the ground. Keep the plant material in clean places.
The cutting board is sacred. Do not to place random items on your cutting board. Generally, a cutting board for herbs should be used only for medicine and not for food preparation. Knives also are best reserved for this special use. At least, you should not cut meats on your medicine-making board, and avoid pungent vegetables. Keep the work area, cutting board, knives, and other tools clean and pure. It is also good to have a pocket knife that is primarily used for harvesting.
Consider the habitat to avoid over-harvesting. Traditionally, the "grandparent" plants (such as those on top of the hill) should be left to continue supplying seed. And, of course, avoid harvesting to the point of detriment to the population. Invasive weeds have a priority for harvest, not only because so many are useful (Japanese Knotweed, Teasel, Reed, Purple Loosestrife, Tree-of-Heaven, Yellow Dock...) but also because it provides territory for native plants.
Basic tools include a good, sharp pocket knife; a pair of scissors or, even better, some pruning shears; and a digging tool. As mentioned, it is best to have a pocket knife for the purpose of medicine-harvesting. Scissors can be useful, especially for processing annual herbs; but in the field it is good to have at least a small pair of pruners. A hori-hori, or digging knite, is an ideal tool for minimal carry. However, it is also possible to use an old screwdriver, piece of rebar, or a trowel with a sturdy fixed-blade. Many cheap trowels are too weak for wild-harvesting and bend or break easily. The hori-hori is ideal. For harvest days I will be providing various tools like spading forks, shovels, machetes, saws, hatchets, axes, pruning shears, loppers, and digging knives. For big jobs (like Japanese Knotweed and Japanese Barberry) we will be using crow bars and digging bars. Especially with heavier metal tools, it can be good to have gloves. Camp-style folding saws can be very useful.
Tote bags are very handy.