Any coin that meets any of the below criteria easily makes the cut:
1) The coin is a clone/tweak of bitcoin.
2) The coin uses centralized checkpointing, "backing"/pegs, etc. Anything centralized.
3) The coin was pre-mined.
4) The coin was ninja-mined.
5) The coin was insta-mined.
...many more easy-to-spot criteria, I'm sure.
6. PoS
7. IPO
8. Extremely fast emission schedule
9. Developer hailed as genius despite few if any previous accomplishments
10. False, fraudulent, or unverifiable back story
11. (Likely bought or purpose-created) sock puppet accounts hyping the coin or trolling competitors
None of these are definitive, but a pretty good point system could probably be created that would be quite accurate.
Closed source,
Closed team,
Marketing budget > development budget
Airdrops/giveaways substantial to distribution
Changes in social contract to benefit a minority
Multilevel rewards
Issuance cliffs/stages
Lottery rewards
Crackpot cryptography claims