Wildcrafting is harvesting a shared community resource, since this resource is shared there are certain rules of etiquette you should follow.
Always ask permission. If you're foraging on private property, always ask permission first, always. Otherwise you could be trespassing. Public lands are fair game, but private property requires permission first.
Do not harvest all available. We need to practice principles of sustainability in that if there is a cluster of wild edibles, you may harvest some of it, but not all. Leave some for others, as well as to let the plant grow back more. This of course varies on the plant. If you are harvesting a berry or fruit, by all means, harvest all that is ripe on the day you visit. But if what you harvest is a leaf, or especially a root, requiring the death of the plant, harvest only in moderation.
Bring seeds. If your harvesting threatens the plant's life, ie in root harvesting especially, considering bringing seeds of the plant you are harvesting and placing them in the hole you create when you harvest. This will ensure the plant's continued existence at that location, allowing continued harvest for years to come.
Following those three steps should help keep the past time of wildcrafting alive and well.