1. Be mindful of what products they have and respond accordingly. Grab some of those adhesive straps for larger bundles of paper goods, jumbo bags for bedding or large toys, etc. If someone is buying infant hardlines items and doesn't have a baby with them, or if they have gift wrap/bags, ask if they'd like gift receipts and show them how to activate that on the screen. Stickers for little people. Very similar to regular checklane, but requires a little more active watching since you don't have every item in hand at some point.
2. ASANTS. My store absolutely does not want anyone but TPS confronting guests. We suggest that they use the hand scanner for items that may be on the bottom deck of the cart (those are the most common SCO push-outs at my store), eyeball for items in the baby seat area, under an infant carrier, etc. "Did you change your mind on (item still in cart and not scanned)?" is generally how I draw attention to those. Definitely harder when coats and purses are in the cart, but there is only so much you can do.
3. Again, probably ASANTS. I greet everyone, ask if they found what they were looking for, ask about Red Card. If there's something unique I can use for small talk, I'll at least try. I frequently make comments to their kids about their cute clothes, most kids light up at that one. I'll play peek-a-boo with babies/toddlers. I have a semi-regular with a very cool purse styled like our pro team's hockey sweater, and I've commented a few times on that. Geeky shirts also frequently get acknowledged. You'll develop your own schtick over time.