If you know how to spore print you can tell a lot about a mushroom for the color of its spore print, also you can tell quite a bit about a mushroom for the color it turns when your bruise it.
the only way i ever pick shrooms myself is when i go with my buddy who is a freakin biology major and is a major shroomer and i let him pick stuff out....the trial and error shroom picking just leads to.....death?