If you’re walking through the woods, and you find a mushroom that makes you think: “wow, look at this [or all these]! We got a potentially awesome meal!” and you want to know which of those mushrooms you could actually eat, then consider picking that mushroom and trying to identify it. Let’s pretend like you know a little bit about mushrooms. If you don’t I’d advise reading this article which really introduces mushroom hunting to the novice. If you do know a little bit, then start with these steps:
1. Observe and note habitat. Macro: Is this a hardwood forest (oak, maple, hickory, basswood, etc.) or softwood (pine, hemlock, spruce, fir, cedar, etc.)? Is the terrain upland, lowland, bog, River floodplains, etc? Does the mushroom appear to be growing from the soil or a log? If from the oil, could it be a buried root? If from the tree, is it a live or a dead tree? Near/on what species of tree (e.g.oak leaves on ground near mushroom)?
2. Collect mushroom by cutting its stem or at least preventing dirt from dirtying up the mushroom(s) en route back home. Consider also brushing the mushroom in the field. Trim off dirty ends of the stem. Place in your hemp bag or Amish woven basket or Goodwill purse or 1987 Minnesota Twins World Champion hat or whatever you’ve got on you. Consider taking a couple. Collecting mushrooms is not bad for the fungi. It leaves a network--a “tree”--of fungi and taking a mushroom is the equivalent of removing an apple from a tree.
3. Look at underside of the cap. Are there gills, pores, teeth, or wrinkles? If it has spongelike collection of tubes (take cross section of cap and this will make sense), it’s probably a bolete, suillius, or tylopilus. If it has gills, what color are they? Same with pores or spongy bottom or teeth or wrinkles. If it has wrinkles it is likely in the chanterelle family.
4. Also consider the stem. Is it thick or dainty? Is it hollow or fibrous or densely packed? Is it long or short? Does it have a large bulbous base? Is it growing from an egg like structure?
5. Cut a chunk of the mushroom off. Look at the flesh that cannot be seen when the mushroom is left in tact. What color is it? What texture when slicing? Squeeze the cap or stem and observe if it bruises or changes colors. Sometimes this will be striking, like after slicing the mushroom in half it will rapidly darken from a white to a dark blue or black.
6. Take a piece or two of the cap. Ideally place an entire cap on a piece of black and white paper. Let sit for three or four hours. Gently lift up the cap and peek underneath. Are there any colored prints left behind? These are the spores which fell from the cap and this is called a spore print. It’s how the color of a spore is determined. If there’s no spore print after a few hours, let sit for up to a day or two and there could still be a spore print left. Past that and typically you have a dried unidentified mushroom you can feel free to just toss into the compost.
Once you have a spore print, you should be able to identify the family and/or genus of the mushroom. Here's a link to a description of the more common families of fungi. In many cases, with all of the information you have collected you could positively identify the mushroom, 100%, at this point. However, this is not always the case. Typically guidebooks will have a "comments" section or "look-alikes" under each species of fungi, which will help you immeasurably in determining how difficult identification should be. For exceedingly tedious families, such as cortinarius, hygrocybe, and even some agaricus, the following identification steps may be necessary.
Advanced identification steps:
Obtain some potassium hydroxide (KOH) and drop a little bit on the cap or stem. Observe and note any color changes.
Obtain a microscope. Collect spores onto a microscope slide. Observe spores under the microscope and note shape, dimensions, any other features (smooth, spiny, etc.).
Step 7: Post-identification
At this point, you may or may not have successfully identified the species of the mushroom. If you feel like you just wasted a lot of time and you're still not sure if you know the mushroom, that is completely okay. Just going through that process will reinforce knowledge and introduce you to the nuances of different mushrooms and their relatives.
I also strongly encourage you to join a mushroom ID social media group or page (check out MN Forager), and post at least three or four pictures (mushroom in natural habitat, top of cap, underside of cap, mushroom cut in half). Note the species you think it is, plus ones you've ruled out and why. Also note what kind of forest you found it in, if it's not obvious from photos. See what other amateur mycologists think.
Also, I strongly recommend keeping a notebook, or several, for jotting down notes on identifying characteristics, where you found xyz, complete with dates. Also, of course, always cross reference your identification books with at least three. Ideally more!