Ted Burke has an interesting rant on a subject dear to my heart: that far too many poems are read poorly. Yet he points out that phenomena like the "Def Poetry Jam" are not necessarily the antidote. I would go further: I feel that performance poetry and poetry slams often undermine the work of poets trying to write something that also stands up on the page.
The idea that poetry needs to be "jazzed up" (sometimes literally--with musical accompaniment) implies some fundamental deficiency with the words standing on their own merits. Yet at the same time, I think this phenomenon of so many good people reading good works badly is equally to blame: it reinforces, and spurs on, the hyperbolic performance of poetry, which distorts the art--making it more like song lyrics or a dramatic script than a publication-worthy piece.
Like my sister, I recently had the privilege of attending a voice workshop with Tom Boyer wherein I discovered many of the techniques of the Bel Canto school of Italian singing apply equally well to spoken voice. Applying this has had a great effect on my reading style: it allows me to tap in to my most interesting, authentic voice--the one I use when hanging out with my family on Christmas morning--even when I'm on stage. Through applying breathing and visualization exercises, I have learned to key in to that space, and bring more of myself to reading my work.
Apart from voice coaching lessons (contact me if you'd like to get in touch with Tom), there is another simple remedy for reading better: connect with the poem, with the words, with the meanings. Enjoy reading a poem--you don't have to sing or flap your arms, but you do have to bring out your enjoyment and appreciation of the work. Savor it. Bring some justice to it--especially if it is your own work.
It can be hard to connect with the enjoyment of the poem and bring that across to an audience if you are not comfortable speaking in front of a group. Much of that seems to subside with practice--but it takes conscious practice, trying each time to get more in touch with the heart of the piece. Reading in a relaxed atmosphere among friends also helps. Ultimately, practicing the same things that don't work over and over will not help, and may hinder--so, seek to consciously gauge and improve your own sense of connecting to the poem each time. For me, there has been a palpable difference through practicing this approach.