I've worked at a few credit unions, so some I know some ways of preventing check fraud! I'm in the USA so what I know only applies here.
Most people know these scams and can avoid them, but a lot of vulnerable people fall for it. Communication with someone who isn't the scammer is the best way to prevent it- whether that's family, friends, or your bank. Sorry this came out so long- there are a WHOLE lot more ways that fraud is prevented from my experience as a teller but it's 3am so I'll shut up!