At StartSomeGood, we pride ourselves on being a truly international platform, so don’t underestimate how far your campaign might reach, and prepare to be upfront about your capacity to ship rewards to supporters around the globe.
Unless otherwise stated, all shipping costs must be borne by you, the project creator. Take care to assess what postal service you'll be using and which countries you can ship to cost-effectively. In your reward descriptions, make a clear statement explaining to supporters which countries you can ship to for free, and which you can’t.
Rather than encouraging donors to "Add $10 for shipping outside of the United States/Australia," you can include a second reward level at a higher donation amount to account for international shipping.