1. They will ask you to donate
2. They will ask for your private key
Feel free to add yours in case there are many more.
Best regards and happy airdrop chase.
It's easy; is it and airdrop? If yes, it's already a scam with centralized funds and no transparency whatsoever in regards of initial distribution so they go against two of the most basic fundamentals of why crypto was created in the first place. It's 2017 and these take steps backwards instead of going forward therefore they shouldn't exist and only crypto-newbies welcome them...
And then there's the fact that account trading is legal (but discouraged) so the owners of airdrops can, and will redeem their own coins to dozens or even hundreds of their own sockpuppet accounts basically hiding the usual premined scam nonsense.
Edit: also, if any project is bound to a single, centralized website (like ICOs or airdrops) none of the numbers should be trusted at all! Only the source code.