Hiya, found these two for you. Hope they will be of little help.
Generally speaking, poetic words make our speech sound more beautiful. They add flavor to any use of the language. Poetic words resemble colorful paintings by outstanding painters.
Poetic words and phrases come from the bottom of heart. Each person adds a bit of his or her own art when using a word of the language.
I, for instance, when reading fiction or poetry, write out the beautiful-sounding words and learn them. And when I want to sound poetic in my mother tongue, try to make use of them, giving a new life to those words and phrases.
Moreover, the other side of the coin is the following: it's, first of all, important what is said, and equally of paramount importance how it is said. I realized the latter (I mean the way we express what we mean, i.e. how it is said) on my own mistake a few months ago after misusing a phrase in English.
So, it's important to think twice when using a word or phrase of the language. Language is a game, a unity of games between language units. Hence, we should be very attentive when playing this game,making good and proper use of language units. Oh, I feel that I am not speaking to the point now.
The sources cited by Raffee are an excellent start. And I second asusena's comment, that how you say something is as important as what you say.
There's some more insights on what makes "beautiful words" in this thread: http://www.waywordradio.org/discussion/topics/beauty-of-cellar-door-minicast/
Also, see Grant's Word Wall (which I have yet to contribute to): http://www.waywordradio.org/word-wall/