This document discusses strategies for preventing homelessness in New York City. It recommends targeting prevention services to communities that contribute disproportionately to shelter entry. Data on past shelter users can help identify at-risk families for outreach. The city purchased data on buildings at risk of foreclosure to provide assistance to tenants. Tracking which households receive services versus those who enter shelters, and comparing served versus unserved communities, can show the impact of prevention strategies. Evaluations with random assignment can also assess causal effects, though results may be controversial and take time.