I've made the mistake of just joining a bunch of airdrops that seemed legitimate without doing enough due diligence. Yes, I've been scammed, but I think it's led me to having a decent system for airdrops. Start with a spreadsheet to track the airdrops, create some filters by labeling columns and filling them in with color if they check off. Social media presence, contract address, token supply, premine % just to name a few, make a column for date of airdrop so you don't forget. Bonus points for airdrops with a team that has linkedin profiles, negative points for airdrops that claim they will hit a certain price, etc. you should do what makes you comfortable or what you're interested in at the least. Happy hunting!