Practice. Get a copy of XE if you haven't already, learn a bit of SQL, and getting a handle of the variations in DDL (Data Definition Language) between the major RDBMS vendors are a just a couple of the critical bits to know.
And knowing the slight differences in terminology- i.e. in Microsoft, a SQL Server instance has several databases. A single instance Oracle has one database containing several tablespaces, generally not separate and independent of each other as with a MS database instance.
Managing the database, backing it up, and restoring are starting points, see the "2 Day DBA" book at http://docs.oracle.com/cd/E17781_01/server.112/e18804/toc.htm
Restore practice is good to have under your belt as well, when a restore and recover scenario is needed that is not the time to dig through documentation or run about making posts asking "how do i do this ...".
I am an Oracle DBA for 6 months as of now. I've only known about Oracle DBA and the job role less than a year and a half. I know what you are going through and how hard can be to find help as a newbie. I started a blog on YouTube that explains the role of an Oracle DBA, what to study, how to study, installations and I'm working on more. I will tell you off top it takes dedication and hard work more than anything. I don't know everything there is to know and have years and years and years of learning ahead of me but what I do know I want to just past it on, so if you'd like you can go to my YouTube page http://www.youtube.com/user/oracledbagirl?feature=mhee, hope it helps.
Edited by: 929602 on Mar 14, 2013 11:14 AM