Simply contact a Domain Provider and request that they submit a transfer for you domain.
Please note that the .DE Registry (DENIC) requires that the Registrar you are transferring your domain to must receive, via fax, a written authorization of the transfer request from the domain’s Registrant (Administrative Contact). This authorization must be kept on record should the Registry request it in the case of a dispute.
This mean you will need to supply the Domain Provider with the faxed request prior to the transfer being initiated.
Unlike .COM, .NET and .ORG, which have a sixty (60) day post registration transfer hold restriction, transfers in and out are not restricted to any type of hold period. This means that a transfer can essentially be performed at any time after a domain is registered.
DENIC also imposes a non-refundable transfer fee on each transfer request, regardless of whether the transfer was successful or not.