You can start here: https://www.nar.org/find-a-local-club/section-guidebook/laws... but basically, don't launch into the flightpath of an airport.

(Many model rockets don't get above 500 feet, so they never can even get into controlled airspace (usually 1200 ft above ground level) unless you're launching at an airport, which can be totally legal depending on where you are - most places have model rocket clubs and you can find where you can launch)