Firstly, congrats on finishing your book of poetry! As someone who studied poetry, I know how hard the craft is. As far as pitching your book, it depends on what you're looking for publishing. As a start, one should submit and have individual poems published to literary journals. Several universities have literary magazines and journals that are fantastic, and offer a lot of exposure to publishers for up-and-coming writers like yourself.
Secondly, you should have an idea of literary journals that publish work similar to your own. Submit your works there. You'll have a higher chance of being published, AND potentially getting feedback. Generally, any remarks back about your work, rather than a denial, is a pretty good sign that you're on the right track. This step also assumes you have not yet been published in a lit mag.
If you've been published, then I really encourage finding the publishers of poets you like, and publishers of writers with similar style and content as you. These publishers have a niche of writers they are looking for, and if your work matches their style, then you're more likely to get noticed and pass the initial round of low-level readers to more higher editors. Most publishers also have submission guidelines and requirements on their websites.
Obviously, just keep submitting your work. Take writing workshops. Take feedback as grains of salt, but also opportunities to improve as a poet. Getting published in a lit mag is no easy task, and publishing an entire book of poetry is an even more ardent trial; however, persistence and devotion to the craft will be your best bet.
Do your research. Most mid-sized and big publishing houses these days only accept manuscripts through literary agents. I'd start with the book Writer's Market, which will outline the submissions policy for each publisher and also gives tips about querying agents.
If you think your book could fit into the YA market, I'd also strongly suggest checking out a Society of Children's Book Writers and Illustrators conference, which many agents attend.
Allison recommends the following next steps: