what is the best method to know SCAM [AIRDROPs] 
PROJECT
almost all of them is scam and just want to take money from investors thats why they created a token . i suggest not to invest in any of them if you are investors try to find a legit project. PROJECTThat is pretty unfair for you to say. First of all, the OP is asking about AIRDROPS, not ICOs/investments. So there is no money to be taken from investors in airdrops.
Secondly, airdrops have been good and legitimate means for coins to promote themselves and ensure wide distribution. Look at Stellar Lumens and look at Byteball (GBYTE). Both are respectable altcoins with growing community, and not a single satoshi ever asked from their users. Of course, majority of new airdrops now are either useless or want your email or wallet address to try and do funny things with them. But do not let 99 bad apples ruin the 1 good apple
