We know it can be time consuming and confusing to set up your shipping zones and rates. However, you must do this before you sell, even if you're going to offer free shipping. So, here are some links and advice to help.
First of all, think about what items you generally ship. If you sell postcards or CD's you may want to select rates for 1st class mail. 1st class international mail is often cheaper than US mail because they don't have the restrictions regarding unbendable packages. Therefore you could set United States as a zone and then just put in 1st class mail rates up to 12 oz. and then Priority rates for 1 lb. and up (in case you sell in bulk)
If most of your items are between 1-10 lbs., you have to decide if you want to go with Priority Mail, Parcel Post, UPS or a combination. Some people use Priority for up to 2 lbs. and then UPS for any weights over that. As far as International Mail goes on heavier items - Remember, 1st class International mail is cheaper (but slower) than Priority and can be used up to 4 lbs. And don't forget to add in the weight of your packing materials!
HERE ARE SOME HELPFUL LINKS FOR SETTING UP YOUR SHIPPING MATRIX UNITED STATES POSTAL SERVICE PRIORITY MAIL CHART UNITED STATES POSTAL SERVICE PARCEL POST MAIL CHART UPS RATE CHART (PDF FILE) FOR DOWNLOAD | 
