You have to first check whether the coins are listed in the market or not. You can also look for its value so you'll have a good idea on how much you'll be willing to sell your coins. Although, there are instances that some coins are not registered in trading platforms so you just have to wait for it to be listed on any exchange. But since we're talking about airdrops, most of them eventually ends up as shitcoins.
Again, you don't have to wait anything to be listed if you want to sell your airdrop tokens on EtherDelta!
Etherdelta (and Decentrex) are decentralized exchanges that work directly on the Ethereum blockchain. All tokens on Ethereum blockchain (ERC-20 compatible) can be traded on EtherDelta without being officially listed. The only thing that matters is that the tokens are transferable and that you know custom token contract address and decimal.