To lock in future earnings through testnet airdrops, first, actively participate in the testnet of promising blockchain projects. Provide feedback and help improve the project during the testnet phase. This increases your chances of being eligible for airdrops. Keep track of the project's development progress and any announcements related to airdrops. Once the mainnet is launched and the airdrop is distributed, hold onto the airdropped tokens. Analyze the project's long - term potential, including its technology, team, and market prospects. If the project shows positive development, the value of the airdropped tokens may increase over time, resulting in future earnings.