simple rule of thumb for airdrop and bounty, don't give money. They should be the one giving you money for supporting their project. I have joined several airdrops and bounties and got coins from them. the real challenge is that most of the coins have no value right now and just have to wait for a nice development or a break out the project will do. and when joing ICO bounties and airdrops never give your private key and password.
This is true. Better wait for the development of the project.
I have joined so many airdrops before as well, some paid and some did not. Same with bounties, some paid and some did not. Most that I received have little or no value.