Research Your Markets
Read at least one copy of the magazine or ezine before you submit. Even if you are not a serious poet, if you are writing poetry you need to reading it, so read the magazines your submitting to. The guidelines may give you specific steps to follow in submitting, but may be open to a variety of poetry content.  Submitting your work blindly to any publication or site that accepts poetry reduces your chances of being accepted, and wastes time and effort.  Serious writers (all who want to publish what they write) know their markets.  Take the time to read all the poetry in the targeted ezine.  After all, reading  poetry is part of learning to write poetry.  And by reading the poetry in these ezines  you are indirectly supporting the markets you wish to crack.

Follow The Guidelines
Follow the guidelines set down in the publication.  If it says "subject header should read Joe Applegate," put Joe Applegate in the subject header, not  "Here's another poem," or something else that shows you were not paying attention to the guidelines.   It is not just a whim of the editor.  Most ezines have filters on the incoming mail that send each post to its proper place.  Chances are, with the volume of mail received, an improperly addressed submission will be buried in with the spam and other unsolicited email.  Maybe not, maybe yours will eventually get read, but why take the chance? 

Also, the guidelines may say to send your submission in the body of the email.  There is a purpose to that (other than the obvious hazard of opening unknown attachments).  All email programs are not the same.  Programs to convert documents don't always work.  If they work, there is always a type of document that they don't recognize.  In a relatively short time everything will work and we will all be happy, but until then, send your work, in plain text, in the body of the email unless the guidelines specifically state otherwise.  Poetry submissions are easy to cut and past.   If you have a hundred page document or if your work is visual and plain text won't do, query the editor first and explain the situation and work something out.  Don't simply send an attachment. 

Send more than one poem.  Give the editors a choice; make it more difficult for them to say no.  If the specific number is not stated in the guidelines, send four.  Three to five is common.

Be Professional 
Even if you're an amateur.  It's easier, looks nicer, and in this case it means, to know the basics.  The volume of submissions to ezines is staggering . (staggering is such a shaky word, fun images come to mind.... and relative)   Work gets overlooked, things become unglued, get messed up.  So don't be pugnacious if things don't go as you like.  Treat negative response for what it is.  If for any reason someone isn't friendly, (professional?) scratch the source.

One other thing, don't include a note telling what your poem is about.  (I admit to this being a personal glitch in my editor persona.)  If an explanation is needed for me to understand the poem, consider writing short stories (Exceptions, yes... yes, ), but let the work stand alone, after all, it's poetry.

So when all is said, it makes sense to do the things to keep  editors happy (at the least, not to antagonize).  Following the guidelines, for one, will keep editors happy.  And reading strong work, submitted clean and neat, will  be cause  for dancing and singing.

On the other hand, if you are really a rebel and can't follow these simple tips, submit anyway. Who knows?