The free PDA-NET+ allows you to use WiFi tethering via USB or Bluetooth connection without the phone being rooted (download > Google's Play Store).
Watch the video below to see how to download and install PdaNet+ if your carrier blocks the app (they'll do that to force you to pay their monthly fee). FlippySize will also show you some of the settings to enable and/or change.
The free version has a usage limit that requires you to restart PDA-NET+ to continue using it. If the free version works to your satisfaction then I'd recommend that you purchase the full version key to unlock the usage limitation. It's a one time cost of $7.95 and is well worth it versus paying your carrier's monthly fees.