1. I spend from 10 minutes to a whole hour, depending on the number of items I have on my grocery list.
2. I use coupons and double coupons if they're available.
3. I actually prefer self-checkout and bag my own grocery, I like to arrange the items nicely inside the bags. It really annoys me when the bagger roughly handles my nicely picked produce and dumps them into the bags.
4. I use plastic, same reason as Shunskitten, I use them as garbage bags. I refuse to use those reusable shopping bags, they carry all sorts of extremely hazardous bacteria and germs including Salmonella and e-coli, unless you wash them between uses.