There is a lot of misinformation out there about copyrights, so I'll try to explain it as clearly as possible.
First of all, the minute you create something in writing, it is automatically copyrighted. Yes, "automatically". Everything that comes after that deals with "proving" the date you created it, but nothing you do will make it any more "copyrighted" than it was the minute you created it.
That's why people say "email it to yourself", because doing this will put a date-stamp on the poem so that if someone else were to use it at a later date, you could show that your copy pre-dates theirs. This is the easiest and least costly way to do it. You do NOT need a lawyer and the laws do NOT vary state to state...they're Federal laws that protect your property...it's why it's called a copy "right", not "copy write."
If you email the poems to yourself, print them out and put them in a binder so you'll have a hard copy. Next, "save" your email to either your hard drive of your internet providers "saved mail" file. Really, that's all you really need to do.
So, if it's so easy, why do publishers make such a big deal about copyrights? Easy: money. It all boils down to money. When someone provides a publisher with a poem, the publisher is about to make an investment in that poem and wants to ensure it isn't challanged by someone else who claims it was "their" poem. So a publisher will take greater steps to prevent law suits down the road. The reality is that the odds of someone stealing your poem and making any money off of it is very, very remote. For starters, there is not a lot of money in poetry, unless the poet is someone who's already famous (Madonna, Paris Hilton, etc.). In those cases, the poem could be junk, but because it was made by "them", it has the value of fame added, and thus is more likely to be "stolen".
So, if you're worried someone will steal your poem, just email it to yourself, print it out, save it, etc. and you'll be fine. Don't spend a bunch of money protecting something that although valuable to you, probably has very little marketing value.
One more word about copyrights: when you submit a poem to a publisher, you should still retain all rights to your poem. What you'll often see is that the publisher will ask for publishing rights, but that's not the same as the copyright. If a publisher asks that you sign over your copyright, go to another publisher, because publishers don't need your copyright, just your permission to use your material and serial rights for future publishing. This is also why you need to tell a publisher if you're poem was previously published somewhere else, because they'll need to contact the former publisher and get permission to use your poem, or at least let them know they are going to republish it, and they will include in the new publication a note saying "as previously published in..."
I hope that clears up the issue for you.
Editor, New Poets Press