Find people who dislike games where winning or losing depends on potting a single ball.
Preach the merits of a game run by points, and can be won, through skill, even if the balls remaining on the table do not offer sufficient points to win.
Learn the proper rules, and print them out for their education
http://www.worldsnooker.com/page/RulesofSnooker
Americans want to bastardize the game with crap like:
Have to hit a rail like in pool.
Thus removing the name of the game SNOOKER
Point out that if they can pot on a snooker table with those tiny pockets a pool table will look like a toy.
Point out that Alex Pagulayan has won the U.S. Open 9-ball Championship, the World 9-ball Championship, a gold metal in snooker at the Asian Games and this year, the Canadian Snooker Championship.
Remind them that lots of 9-ball players have come from snooker and done reasonably well:

Tony Drago, Marlon Manolo, Allison Fisher, Karen Corr, ad infinitum
So it is an alternative way to improve their play, whatever game they play.
Let them google videos to learn about the game
Steve Davis The Champions Way
Jack Karnehm Understanding Modern Snooker