Well-grown, quality cannabis buds should have a pungent, identifiable smell — that skunky aroma that ranges from slightly sweet to earthy to diesel-like — indicating high terpene content. Alternatively, inferior buds often lack any smell or smell similarly to hay or alfalfa, a sure sign of poorly grown and/or cured cannabis.
For reference, rich scents like coffee and chocolate are typically indicative of an indica strain, while bright, acidic citrus notes are generally characteristic of a Sativa. Hybrid strains will likely contain components of both profiles.