two options, hard drive or migration assistant
Migration Assistant
After your Mac is up and running, with at least one user account, you can use the similar Migration Assistant app to transfer those same categories, with the same restrictions. This is mainly used to move an account from one Mac (or it’s backups) to another Mac that’s already set up. (Accounts transferred this way may have problems, especially permissions problems with files already on other drives, including backups.)
If you have any user accounts on the new Mac with the same name as any you want from the old Mac, there's a conflict. See the pink box in the Using Migration Assistant page below.
Note that user accounts transferred via Migration Assistant may lose permission to see and restore from files on other volumes, including backups.
But if you're already got data you need to keep in any of those other accounts, see Transferring files from one User Account to another.
For details and instructions, see the appropriate page:
Using Migration Assistant on Mountain Lion or Lion
Using Migration Assistant on Snow Leopard or Leopard
Using Setup Assistant / Migration Assistant on Panther or Tiger
http://support.apple.com/kb/HT5872?viewlocale=en_US
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