To remove apps from your iPhone press the app icon until it starts to shake or jiggle. At this time an “X” will show up in the upper left hand corner of the icon. Click on the “X” and a prompt will show up asking you if you want to delete it. Choose “Delete”. This will remove the app from your iPhone, but to keep it off, you will also have to disable the app in iTunes. To do this, open iTunes and go to iPhone>Applications, find the app you want to remove and de-select it in the Sync Applications list to make sure it doesn’t sync back onto your phone.
If your iPhone has been jailbreaked, you may need to go to Installer or Cydia in order to remove the app. Choose the package manager and select to uninstall the app that way. You should then proceed to iTunes and de-select it in the Sync Applications list.
Resource: Dummies