[hpman77]

In spain most shops will give you only plastic, and without any extra cost (you don't pay bags).

Now some shops are beginning to sell their bags, so you take your own bags, or you pay 3 euro cents for each bag.

About carts... small shops have their carts inside the shop so nobody can steal them, but big malls have the carts parked outside and they have some kind of a lock that ties a cart with the previous one on the file. You insert a coin (usually 50 euro cents) and the lock is freed so you can use that cart. When you finish, you move that cart again against another one, and plug the connector of that cart inside your lock, dropping your coin back to you.

Hard to explain, but I can't find better words, sorry.