Have a good application that asks for current and possibly previous employer, current and previous landlord.. Follow up on those, and be skeptical about them. Google the names and numbers, and try to get phone numbers not from the tenant (i.e. if their employer is The Calgary Herald and the manager is Bob, call the main line asking for Bob rather than the # the tenant gave you). Does the landlord phone number show up in Google as having other properties? If not, maybe call them pretending to be a renter asking "if the place they have for rent is still available". Sketchy tenants will give their buddy's number as a employer or previous tenant reference.
Credit checks work pretty well as well, can sign up for something like
https://www.tenantverification.com
As far as scams go, as mentioned if it seems fishy, it probably is. If someone wants to give you a money order and get some cash back, that's a classic scam. I only take security deposits in cash or a certified cheque if they have the receipt for it as well.