Composers who write their own lyrics and libretti are a stand-alone breed. Irving Berlin? Wagner? If you are one of those, then go ahead on! The rest of us need a good writer, either six feet under or above ground. My first rule of thumb: you’ve really got to love and relate on the deepest and most personal level to the words in question. If you feel at any point that this is not the case, then you need to move on. Finding texts that hit you in this way and get the musical juices flowing can take a lot of hunting, but you will know when it’s right.
From my own experience I sense a connection between composing for visuals (i.e. ‘film scoring’) and setting words to music. In each case the extra-musical material helps give you the form. I am a programmatic guy; I like to tell stories musically and have no guilt about doing so. Others do, or are less inclined in this manner. Just to be provocative, think about Beethoven. There was a guy whose music fights the text in question every step of the way; to this day I can’t listen to Missa Solemnis—the music and the words are working at cross-purposes.
In my own case, I will just flat-out state that composing purely instrumental music is far more challenging. Visuals, or images triggered by words, provide you with a scaffold to hang the music on. This can become a crutch. At the current time I am making a conscious attempt to get away from setting texts, as I feel I’ve become dependent on that formal ‘bump’. (Note: watch out for that copyright stuff; I got into a very frustrating situation a few years back regarding texts written in the latter part of 19th century that I assumed were in the public domain. They weren’t; the copyright dated from when the edited texts were first published, in the 1930s, and the heirs of the editor could not be located.)
Then there is the question of who is actually going to sing/say your chosen words. This makes a huge difference! As my friend, composer Van Dyke Parks, once said to me when I was trying to find a vocalist: "There are a lot of canaries out there." Indeed there are, and they are not all created equal. I’ve been to the mountain though, so I have some idea of what is possible. I was lucky enough to have the sublime Canadian mezzo-soprano Catherine Robbin record my setting of excerpts from the journals of John Muir, titled Range Of Light, for New Albion Records. True story: I walked into the recording booth and the engineer turned to me and said, "They’re tuning to her!" Now that is high praise for a vocalist. Indeed my attempt to ‘serve the text’ was fulfilled by Catherine Robbin’s incredible intonation and the clarity of her diction. In the case of Range Of Light, the subject matter of the text is California’s Sierra Nevada mountains. I have experienced in those mountains some of the same things that John Muir did; this made the compositional process a labor of love, and I hope that some of this comes through in the music.