Written by Topher Kessler
Apple has recently updated their knowledgebase documents with an article on internet tethering via iPhones. Being a relatively new feature for iPhones, and not being supported by all carriers, troubleshooting this connectivity option can be frustrating to people.
The knowledgeable article covers system requirements, iPhone settings, computer settings, using Bluetooth, and information on adjusting network service priorities to ensure the tethered connection is the one being used.
Read more on troubleshooting internet tethering here: http://support.apple.com/kb/TS2756