I took some notes during TUAW’s Dev Clinic discussion on the process to compile your app and upload it to iTunes:

• Application Target
  • Make sure you are using the “release” configuration, and not “debug”
  • Base SDK: iPhone Device 3.2 (or 3.1.2 or 3.1.3 for Universal)
  • Architecture: armv7 (you’ll have to select “other” and type this in)
  • … for a universal app select “armv6 armv7″
  • Code signing identity: Distribution
  • Targeted device family: iPad (unless you are doing Universal)
  • Deployment target: “iPhone OS 3.2″ for iPad-only, “iPhone OS 3.1.x for Universal”
  • Icons: use a 72×72 icon (not 48px as some have said), you may or may not want to include a 57×57 icon
• Signing and Uploading
  • Set your configuration to “Release” in the Target Info window and in the Project window
  • Compile for the device, not the simulator
  • trash your previous builds (the entire build folder, even!)
  • double-check your code-signing identity, update your distro provision if necessary
  • after you compile, locate the binary using Products < [app] < Locate in Finder
  • zip up the app and submit it to apple

Other helpful resources:

• Re-signing applications http://www.tuaw.com/2010/02/09/sdk-devsugar-re-signing-applications/
• If you want to triple-check everything, you can use this hint to try out your distribution build on your device: http://furbo.org/2008/11/12/the-final-test/