How do you come up with pricing for shipping

I've got a client who is setting up an ecommerce store. What's the best way to come up with shipping prices?

Is there are plugin or something that can automatically calculate what to charge for shipping? Is there a better way to come up with pricing for shipping?

Thanks for your help.

Bump. Any suggestions?

Depends on what you use to ship. Ebay will sometimes do it automatically, but for non-preset packages, you need to measure the measurements and manually enter it (although you could probably script this easily) on the mailing company's site.

For example. I sold a large package the other day. I just measured out the measurements, put them on USPS and it was pretty accurate. You might want to add in a few bucks above the estimate to be safe.