Is the domain registered here at DreamHost? If it is, then as far as I know, only DreamHost support can move domains directly from one account to another. I suggest you contact them after your friend has established his account and ask for the domain to be moved across.
If the domain is not registered here at DreamHost, the procedure may be as simple as removing it from the DreamHost hosting system under your account and re-adding it under your friends account.
Note: The above procedures are only concerned with transferring the domain between accounts. The contents of the domains web accessible directory will need to be manually moved across using FTP or WGET or whatever.
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