smell has alot to do with it, stronger smelling weed can sometimes infer higher quality weed. another method i like to use when inspecting is hold a flame (lighter, match, etc.) up close to the bud and examine the crystals formed on the bud itself. shinier, gllistening crystals will provide the most thc content, and densly populated fat crystals will provide the most taste. at least from what ive dealt with.