Even if you are sure what kind of mushroom it is, still... take a spore print! It's easy to do. Just carefully cut off the caps of two of the mushrooms in question and lay each one (gently) gill side down on two pieces of paper, one paper white, the other one black. Let the caps sit for 2 - 6 hours. Carefully lift them from their papers and see what color spore print they left. Spore prints are the patterns left on the paper from the spores dropping out of the mushroom's gills. Different mushrooms have different colored spore prints, black, purple, rusty, bright yellow, brown, white, etc. That's why I use both black and white pieces of paper. Any really good mushroom guide should list what color a mushroom's spore print is. When in doubt, take a spore print. Mushrooms can be tricky so be safe whatever your intentions are, neither your next meal or next high is worth suffering a painful death. Know what the mushroom you are after looks like, know what it's "look a likes" look like, know all their spore prints, and know their growing habits and habitats. I'm no expert with mushrooms, I just know a handful of them well and have the confidence to gather and use those for food. Start out with getting to know just a few mushrooms real well.