Start Firefox in Private Mode Automatically

Problem: You don't want to keep pushing Ctrl + Shift + P every time you open Firefox.

Solution: Tools → Options → Privacy (tab) → check "Always use private browsing mode"

Not Syncing Calendar after Jelly Bean Update

Problem: You just upgraded your Galaxy S3 to Jelly Bean and synced your Google account, and your Calendar entries are missing.

Solution: Go to Calendar → Click on "Calendars" (top center) → Check all the calendars you want → click "Done" (top R)