How do you avoid counterfeit electronic tickets?

I've actually had a problem with a ticket I bought on some sketchy site, so I know what you're talking about. For e-tickets (concerts, flights, etc), always buy directly from the official seller or recognized platforms, never from sketchy little sites or dodgy listings. Check that your confirmation email arrives, that the details match up (date, time, seat), and watch out for prices that seem way too good to be true. If you have them as PDFs, keep a copy and the email - it helps if there's an issue when they scan your ticket.