How do you dispose of garter snakes properly?

You don't. You catch it seeing as how its not posionus and relocate so that you both win. There is no need to kill it. Take it far enough and it wont come back. But he is not harming anything and is actually helping your yard by getting rid of rodents and other vermon so leaving him would be benificary to you to. Maybe this URL will help you... http://www.ehow.com/how_2079050_build-funnel-snake-trap.html