If I see some airdrop announcement thread firstly, I check how much effort they put in it. If it is just copy-paste from some other airdrop or just some random text or something like that I automatically skip it. But if their thread looks legit to me and that they actually put some effort in it, then I check out reply to the thread to see what other people are replying. Then if everything seems okay, I check their website and other links they provided. Also be very careful, if thread seems scammy don't click on any links, especially do NOT download  their so called "wallets". And lastly check which information they want you to provide.

If it's only your ethereum address and bitcointalk profile link that is okay, with that they can't do you any harm. But if they ask for more personal information then be sure that they are legit and that their airdrop is authentic

Be safe and check twice!