Take the time to inspect your boat and trailer while removing any plants and animals before leaving the ramp area. Pull plugs and clean drain and dry your boat, live well on land before leaving. Empty your bait bucket on land far enough away from water that it can't get back into it. Trying to feed the fish by releasing bait into the water only hurts the environment. That's why it's illegal in some places.
Rinse off your boat's propeller, trailer, buckets, floats, gear, you name it...the works. High pressure washing works best. Finally, air-dry your boat and equipment for as long as possible before entering new waters. And before you transfer your boat out of state you may need to get a certification or affidavit that certifies your boat, trailer and other equipment are invasive free.