I have been writing more then half my life, and I have a large collection of poems, transcripts, stories etc. that have accumulated over the years and I want to protect my rights to them for future use.
The moment you write the first letter of your poem, it is copyrighted because of the new copyright law.
The copyright law could be strengthen by registering it in WGA or copyright office - but that is generally not needed unless you are going for large scale publishing.
The "mail it to yourself" is a myth. It does nothing to copyright your work nor will it stand in court