There so many of them: advertising of different kind, bounties, participation in conferences, other events, airdrops.
And I think airdrops are one of the most useful way to spread awareness about the projects. But as everything, they should be well thought out. Also, it does not make sense to conduct airdrop on its own. It should be done along with others activities I have mentioned earlier.
Another thing is that there are a lot of weak projects which carrie out only one or two activities like airdrop or/and bounty, since they aren't able to do more than that. Well, in this case, their coins will be sold immediately as they appear on the market