Airdrops are free coins or tokens given to a specific number of people (random) and are usually used to promote a new coin into the market. Each coin or project have its own rules and guidelines to receive the free coins (Airdrop).
The easiest way to find out about these airdrops is usually to join a group or a channel that list these Airdrops, so that you will always find ongoing airdrops without the need of searching through the whole web for it.
Corrections needed on this, you would have been better off calling this thread an Announcement.
Airdrops are not given to a random number of people, it's actually very specific. Airdrops are tokens/coins given out in the exact number of tokens/coins that exist currently on a blockchain that is a target for a hard fork. Anyone who has a wallet with private keys for the target coin will receive the same number they own in the new coin to allow them to adopt the new blockchain and coin if the hard fork is successful. This is called an Airdrop.
Most of what you describe above is an initial coin offering (ICO), which has nothing to do with a hard fork. When a new token/coin is started these coins are either available for purchase or available to be mined. And if you are working for the new token/coin to advertise for them you may receive an allotment of coins as compensation for your advertising work - this is called income...not an airdrop.