Look for moments of unpredictability and creativity while also maintaining continuity.
Avoid pieces that rely on repetition. Look for pieces that inject rhythmic variety with techniques such as mixed meters, polyrhythms, syncopation and rhythmic variety within the parts of a given section.
Look for harmonic motion that appropriately challenges the players to expand their harmonic vocabulary and comfortability. Consider tonalities outside the Major/min sphere.
Look for authentic representations of cultures outside of your own so as to provide both a cultural mirror and a cultural window for your students.
Look for longer or asymmetrical phrases, melodies that allow for student-led decision making, and diverse contours of melodies.
Look for pieces that fit your soloists but avoid pieces with might cause students to disengage during rests. Look for works that maximize engagement for ALL students.