You cant really separate which airdops is really legit and which is not...  Even us we get victims of it...  But you will not know it if you didn't experience it to happen to you...  Try to participate in every airdrop as many as you can and you will surely prove it to your self that almost half is scam and half of it is legit...  Well we cant control it because the coin here is free and the less efforts we exert the hogh chances that it is scam....