You can not be 100% sure about the real ones and sometimes, it's the one that you don't expect to make profit from that is going to give you the profit you don't expect.
Airdrops are based on luck and possibilities, most of them looks so real, but end up disappointing people that participated. Very few of them project owners are out for the real deal with strong commitment to their project. Some are out to build their media handles only, others to scam unsuspecting participants.
You just need to be very careful and always DYOR and be sure you're following your instincts and not just what someone else says. Above all, don't cast your hope on it or participate with more resources than you can loose since some airdrop tasks are capital involving.
Airdrops pays, but you're not entirely sure the one that would pay well, so it's very much okay if you engage in more of them to increase your chances of making profits
To know a real airdrop (not 100% tho), you need to follow up the project's update. Do not just keep participating in the airdrop when the project you are promoting is not even showing a sign of growth and they are not developing their project. Follow every information on their social media accounts and also ask questions in their most community.
You can still do all these and it would still fail, but it surely helps, and the quality of information shared on their handles matters a lot also and can help you determine if they're building or just marketing a baseless project.
Their partnerships are also key to the success. If they're able to secure good partnerships with well meaning crypto enthusiastic companies, it surely shows they're going somewhere good.
Come to think that if people would turn out that they do know on whats fake and whats real then we do only have few airdrops that could be seen in the market, on which this simply means that we would really be dealing mostly legit projects in the market but thats not the case that we are facing on but rather it is really that the opposite on which there are really tons of fake projects that we do see in the market and if you wont really be that careful then you are just basically wasting up your time on dealing up with these projects and the worst you might that be ending up on spending up some amounts when it comes to gas fees or any other transaction related kind of tasks on which we know that there are really certain projects who do have that kind of steps needed for you to be that eligible for the drop.
The key on here so that you wont really be that easily get scammed or get involved with those fake airdrops.
1. Avoid sticking with copycat projects. Always those unique or first ever type in the market always have that high probability on succeeding
2. Obvious farming like spending up something for diamonds,vip and other
3. Too much hype (Already learned from this)
4. Unknown Devs
5. Shit UI/UX looking
6. Shit tokenomics
Its really that impossible that you wont really be able to determine it out not unless if you are a complete newbie into this space then most likely you would be skipping out these things
but if you've been here on this market for a while then im pretty sure that you are wary with these stuffs. It is really just that there are certain individuals who are really that too lazy
on trying out to make those kind of research and verifying things and keeps on engaging despite of those obvious things thats in front of them.