Too many open accounts, not enough open accounts, too young avg account age, no revolving credit, high debt to income ratio, guarantors opening accounts on your behalf and defaulting/being delinquent, sharing credit accounts w/ others that don't pay on time, too many hard inquiries. Plus others I can't think of right now; I think that's sufficient. It's waaaay easier to have good/avg credit when you haven't lived as an adult for a significant amount of time. Not saying this is the case with anyone, just things I've learned from experience. My credit was garbage for almost ten years from my parents making poor financial decisions and it's just now respectable after 3-4 years of working on it incessantly.