Which shipping options (i.e. carriers) do you offer to your customers shopping on you website? Which shipping carrier do your customers seem to like to use most for delivering their packages to them?
I wrote a blog about this last week: http://www.ecommerce-blog.org/archives/best-shipping-practices-for-ecommerce-websites/ Personally I recommend UPS or Fedex.
UPS and Fedex seem to be most popular. You'll need to check their biz rates to see what helps your margins as well. From a shoppers perspective, I haven't experienced problems with either so I don't care what's offered to me (as long as it's cost effective).
It depends on what type of products you want to ship. Low value items are usually shipped via USPS or UPS Ground. Fedex Ground is a little more expensive. FedEx 2 day service seems to be cheaper than the UPS alternative.
You can't beat Australia Post - competitive price, no contracts, no minimum spends, they service the whole of Australia, Post Offices are everywhere. They are perfect for B2C. We've been using them for years now (registered post, platinum express...etc), and have tried a lot of other courier companies but they can't compare. Fedex and the likes are too expensive, require contracts, don't delivery Australia wide, don't delivery to PO boxes, re-delivery (if the customers is not at home the 1st time) is problematic.