Like things together.
Meats with meats
Cold stuff with cold stuff
boxes with cans
Make your base (when you can, usually in paper. Sometimes works in plastic) Boxes on 2 sides cans in between, lighter stuff on top of cans.
Fruits and vegetables go together.
Try to keep the dry stuff away from the wet stuff.
Chemicals/nonfood stuff in their own bag. Sometimes the customers don't care if it's with boxes/cans.
never put the bread with scented stuff.
make sure nothing heavy is on the eggs. Hell, in my store the eggs usually have their own bag by themselves; unless there's bread.
If you're unsure if anything should be bagged, just ask. (Gallons of Milk, heavy stuff, 6 packs of soda/alcohol, toilet paper.)
and squishables. The stuff that's squishy that can break or whatever. Don't put that under the heavy unsquishy stuff.
Don't know about you but I've been bagging nearly a year, and I'm early twenties. It's like impossible to switch departments here because someone else from a different store swoops up any open position by transferring.