If you know what yarrow looks like it is easy to spot in the summer and spring. I have harvested tons of it, made tinctures, smoked the leaves, flowers, made tea, eaten it raw, you name it, it is really good for you. never got any headaches as for the euphoric qualities of it, i have not really experienced them although ive heard of it too, i heard its affects can only really be felt with mixed with booze so there ya go. my goal is next year to brew wine and beer using only wild plants that i collect. there are some amazing edible plant wine recipes on jacks website.
asfor mint there are tons and tons of different kinds. the most common being peppermint, spearmint, wintergreen, sage, catnip and hyssop, which is mentioned in the old testament.
Personally if i were to use mint, i would probably go with wintergreen(which im not sure is really in the mint family), or the sage that i already tried using. maybe some hyssop.
as for my beer (a slightly spiced barleywine ale) called "Double Dragon Barley Baby" DDBB it is starting to slightly bubble, and the foam on the head is starting to form.