Institute and change existing policies that are aiding in human overpopulation. Focus on USA first, avoid the American status-quo: Do as I say, not as I do.
Reasons:
With climate change and increased pollution we are likely to see famine, this will lead to war (human population reduction via mass violence).
We have entire communities that have been discarded (jails). Have less kids, focus on the ones you have to ensure more than survival, development into successful adulthood.
How to accomplish:
Investigate: Start investigating human overpopulation and determine the most successful population levels.
Use education and media to gain attention to the problem and the benefits of reduced human populations.
Stop paying people to have kids (Tax codes / welfare).