you can tell by the look and feel if it's good.
cheap nasty weed is dry, crumply, seedy, and brownish in color. sometimes it's not too crumply, but if it's got seeds, it's brownish, and kinda cheap, yeah, it's shwag.
good, 'dank' weed smells kinda like dead skunk mixed with pine, it's a smell that once you know it, it stays with you. it's color is very green with a lot of orange/amber hairs. it should be covered with little crystals or tricombs. it'll be sticky. it should be dry and sticky. not moist. there's a difference and learning it makes a difference not only in quality but quantity. moist buds weigh more, and since dank is priced by the gram in a lot of areas, a dealer selling moist buds can make an extra 100 bucks per o easy, ripping off who he suspects are his more unknowing customers....
the giveaway is the smell, and texture, at least for me. good weed has a distinct smell to it. they all vary somewhat, but i'm telling ya, once you know the smell of good weed, it stays with you forever.....