If you have a second user account on your Mac in which you have done some significant work, you might at some point wish to combine it with your main one. Unfortunately there is no quick way to do this, and will require some manual transferring of files, contacts, and other information, as well as remembering which of these you need to transfer.

To combine accounts, first be sure you have a full and restorable backup of your system using Time Machine, or a system clone, and then do the following:

1. Export centrally managed content first, so log into the account you want to delete, and then export things like contacts and calendars to the account’s Desktop, or another convenient location. You can do the same for Safari bookmarks, and those from other browsers and contacts managers. Keep in mind this will have to be done manually, and done before you proceed with the next steps, so be sure you have all items identified and exported.
   

   Exporting data from all programs with centrally-managed content (such as Contacts) will ensure they can be imported in your new account.

2. Log out and then into the user account you wish to keep. Note that this account will need to have administrative status.
3. Go to the Users & Groups system preferences and delete the first account, but choose the option to preserve the account’s home folder in a disk image (this should be the default option).
4. Go to the newly-created Macintosh HD > Users > Deleted Users directory in the Finder.
5. Open the disk image you will find in there, which should be the name of the deleted account—it should mount in the Finder as if you have attached an external drive.
   

   When you delete a user, you can save its home folder contents in a disk image, which will make accessing the user’s files easier (click image for larger view).

6. Copy any files you need from this image to the current account. Note that if the image’s contents are too large to copy without filling your hard drive, then you may have to first use an external drive to copy the deleted account’s disk image to, followed by deleting the account image from your hard drive, and then open the image on the external drive.
7. Access the exported contacts, bookmarks, and calendars you did as the first step (which should be in the specified location on the disk image), and import them into their respective programs.
8. When all files are copied from the previous account to your satisfaction, then you can eject the disk image and delete it.

This routine will combine the user-created files and folders from the old account with the new one; however, some features like keychains cannot be exported and then combined with that of your new account. Therefore, you will have to re-save your passwords from the prior account.