Just research the project as much as you can, and you will likely find some red flags if any are there... so what the coin is supposed to do, the team and their history, quality of website is often a good indicator, white paper full of buzzwords but little of any substance etc... the list goes on, but many scams are quite easy to spot. Those that ask for KYC for airdrops are probably worth avoiding as well - not necessarily scams, but certainly not worth the risk.