I am not a database mirroring expert, but a while ago I have set up database mirroring between two of my machines. I collected the steps that I followed in the following script:

-- This script illustrates how to setup database mirroring between two machines.
-- The script assumes that the principal machine is SQLPRINCIPAL and that the mirror machine is SQLMIRROR.
-- Also, a dbm share will exist on SQLPRINCIPAL, and SQLMIRROR can read and write from it.

-- on SQLPRINCIPAL:
--
CREATE MASTER KEY ENCRYPTION BY PASSWORD = 'Af01AufdSL';

CREATE CERTIFICATE cert_dbm_principal AUTHORIZATION DBO WITH SUBJECT = 'DBM - Principal';
BACKUP CERTIFICATE cert_dbm_principal TO FILE = '\\SQLPRINCIPAL\dbm\cert_dbm_principal.cer';

CREATE ENDPOINT dbm STATE=started AS tcp (listener_port=5022) FOR database_mirroring (role=all, authentication=certificate cert_dbm_principal);

CREATE DATABASE dbm ON PRIMARY (NAME = br_dat1, FILENAME = "c:\dbm\dbm.mdf", SIZE = 8mb) LOG ON (NAME = br_log1, FILENAME = "c:\dbm\dbm.ldf", SIZE = 8mb);
BACKUP DATABASE dbm TO DISK = '\\SQLPRINCIPAL\dbm\dbm.dmp' WITH FORMAT;

-- do the mirror steps before returning here.

CREATE LOGIN l_dbm_mirror WITH PASSWORD = 'Neufd1C';
CREATE USER u_dbm_mirror FOR LOGIN l_dbm_mirror;
CREATE CERTIFICATE cert_dbm_mirror AUTHORIZATION u_dbm_mirror FROM FILE = '\\SQLPRINCIPAL\dbm\cert_dbm_mirror.cer';
GRANT CONNECT ON ENDPOINT::dbm TO l_dbm_mirror;

ALTER DATABASE dbm SET PARTNER = 'tcp://SQLMIRROR.domain.company.com:5022';


 
-- on SQLMIRROR:
--
CREATE MASTER KEY ENCRYPTION BY PASSWORD = 'Dgc6a3um';

CREATE CERTIFICATE cert_dbm_mirror AUTHORIZATION DBO WITH SUBJECT = 'DBM - Mirror';
BACKUP CERTIFICATE cert_dbm_mirror TO FILE = '\\SQLPRINCIPAL\dbm\cert_dbm_mirror.cer';

CREATE ENDPOINT dbm STATE=started AS tcp (listener_port=5022) FOR database_mirroring (role=all, authentication=certificate cert_dbm_mirror);

CREATE LOGIN l_dbm_principal WITH PASSWORD = 'Sc6d061t';
CREATE USER u_dbm_principal FOR LOGIN l_dbm_principal;
CREATE CERTIFICATE cert_dbm_principal AUTHORIZATION u_dbm_principal FROM FILE = '\\SQLPRINCIPAL\dbm\cert_dbm_principal.cer';
GRANT CONNECT ON ENDPOINT::dbm TO l_dbm_principal;

RESTORE DATABASE dbm FROM DISK = '\\SQLPRINCIPAL\dbm\dbm.dmp' WITH NORECOVERY;

ALTER DATABASE dbm SET PARTNER = 'tcp://SQLPRINCIPAL.domain.company.com:5022';

 


-- Additional commands
--
-- to remove mirroring, issue on either partner:
ALTER DATABASE dbm SET PARTNER OFF;

-- to check the state of mirroring, issue:
SELECT * FROM sys.database_mirroring;