This guide applies to the Chicago Region and is not complete for other regions. Disclaimer

Key to Mushroom Genera with Free Gills.
Step 1: Spore Print Color

White. Ring present or absent.

Pinkish to salmon. No ring on stem.

Greenish to olive gray.
Go to Chlorophyllum

Reddish when fresh, drying darker.
Go to Melanophyllum

Black, inky.
Go to Coprinus

Chocolate brown.
Go to Agaricus

All images by Patrick Leacock unless noted.