Recently I purchased a new MacBook Pro laptop. Here’s how I synchronized my iPhone 5 and my iPad Mini to the new computer. Both were mated to my previous MacBook Pro.
By design your iDevice can only be synced with one computer at a time. Also by design the synchronization process is one way: from computer to iDevice. This means that photos or music on your iDevice that aren’t backed up will be lost if you just sync with the new computer.
Make a back up to the old computer. Better safe than sorry.
Authorize iTunes on the new computer. With iTunes running select “Authorize This Computer…” from the “Store” menu. This allows your new computer to access any purchased music, movies, books, or apps.
Turn automatic synchronization off. Open up “Preferences” in iTunes and select the “Devices” tab. Once there check the “Prevent iPods, iPhones, and iPads from syncing automatically” option.
Download all purchased content. Visit the iTunes Store (sign in with your account if necessary) and select the “Purchases” option from the Home screen. For each category (Music, Movies, TV Shows, Apps, and Books) click the “Download All” button. Depending on your past purchases this may take a while. The idea here is to have any and all purchased content that might be on your iDevice on the new computer before syncing it the first time.
With iTunes running connect your iDevice. Do not sync at this point.
Right-click on your iDevice in the in the sidebar and select “Reset warnings”. You may need to click on the ‘View/Show Sidebar’ menu option to see your device,
Right-click on your iDevice again and select “Backup”. This will create a new back up of your device on your new computer.
Right-click one more time and select “Restore from Backup”, select the backup you just made. When prompted to create another backup, decline. This will restore your iDevice using the newly created backup.
You MUST now sync your iDevice to restore your iTunes content, which you will select from various tabs in iTunes. You’ll get a popup regarding your contacts and calendars asking to merge or replace. Select “merge”.
There is no step 10. You are done. You iDevice should look just like it did when you started, with no data loss.