Look you can try anything you want, nothing will work if you're SCO ™ isn't paying attention. I don't get into a 20 minute convo with every guest, but I say hi to every single one. That way they know I'm present if they need me, but also that I'm watching.
Don't stand still. Walk up and down the row, making yourself visible for the reasons I just mentioned. Glance at the screen, and make sure the total looks roughly accurate for items in cart. You don't need to whip out your calculator, but if they have a Dyson, and their total is $15, something's not right.
BOB and LISA: When I see BOB I walk up to the guest and say "just an FYI, you can use the hand scanner for that *insert big item*". legit guests appreciate the tip, scammers know I'm watching them.
Coupons: DEAR LORD LOOK AT THE COUPONS!!!! Sco stupidly doesn't show a list of coupons used anymore. Tape over the coupon slot, and have all cashiers verify coupons as they would at a regular lane, and then take the coupons and deposit them at the nearest lane.
Try to avoid getting in an extended convo with one guest about an issue-- scammers will strike while you're not watching. I try to glance around as I'm talking to a guest to keep my eyes peeled, but you can only do so much. To this end, don't leave SCO unattended, ever.