My first response would be, is the work playable? Is it right for my style? Can I get behind it? Having premiered works by Libby Larsen and Judith Zaimont, I am well aware of the problems in tackling new works. You want to satisfy the composer, the audience, and oneself.
One spends a lifetime learning Beethoven and Brahms, trying to stand in their shoes to re-create what they wanted. With a living composer, it is wonderful to be able to phone and discuss issues. I sometimes play the work in question over the phone! Nowadays we all have major challenges before us—the public is more savvy, also more blasé. It is important to link to exhibits if playing in a Museum, or on a campus, presenters are desirous of linking the piece to their setting.
We need to play new works, commission composers, because how else can our art of music survive? Music matters!