Wheels on the outside, frame in the middle. Mini d-lock between the drop outs (or cardboard, or similar). Add cardboard to everything if it's an unpadded bag. Don't have anything moving around (use towels or clothes to give everything "it's place"). Use compression straps on the outside if your bag is marginally too big for your bike (compression straps help with keeping things secure/immobile).
Add your address somewhere and add a fragile sticker or two for good measure (and pray to the luggage throwing gods).
Wheels on the outside, frame in the middle. Mini d-lock between the drop outs (or cardboard, or similar). Add cardboard to everything if it's an unpadded bag. Don't have anything moving around (use towels or clothes to give everything "it's place"). Use compression straps on the outside if your bag is marginally too big for your bike (compression straps help with keeping things secure/immobile).
Add your address somewhere and add a fragile sticker or two for good measure (and pray to the luggage throwing gods).