I'm not going to talk about cutting lines (I fucking hate people doing it, and never do it), but I like the shops that have a unique line for multiple check outs. It seems longer, but it's faster than multiple lines for every check out.
I used to steal food by dividing my groceries caddie into two sections. In the lower section I used to put the expensive things (chinese food, meat etc...) then cover it with a bag from the shop (big plastic bag) then in the higher section put some cheap things (fruits, milk, toilet paper).
I'd take out the big cheap things, put them on the belt then take out the big plastic bag, and the cashier wouldn't even try to check my caddie.
(those caddies)
The thing is to go a few minutes before they close the shop, because the cashier only wants to go home and doesn't want to argue and look at your big bag.
If you get caught, it's around 9/10pm and by only saying sorry I just forgot I had those other things, I'm tired... people usually understand, plus you already paid some things so it's not like you stole everything, and for them it doesn't make sense to only steal a few things and pay others.
I did it for three years and never get caught. At the end I used to steal expensive things like good cheese, Foie Gras, smoked salmon, then one day I started to feel fear and never did again.