Record yourself playing a song, either from the band method book or sheet music. This may be either video or audio. See Miss Helms if you require assistance with this.
Watch/listen to your recording. Assess yourself and be prepared to discuss your performance on the following criteria:
(1) Correct notes and rhythms
(2) Tone quality (sound your instrument produces)
(3) Dynamics (how loud or how soft)
(4) Articulation (tonguing/slurring, etc)