When the melody goes up crescendo. When the melody goes diminuendo. The change will be small unless the composer indicates otherwise. The other exceptions are clearly marked in the score. The last note in a melody before a rest is played gently unless the composer indicates otherwise.
Please check out the following recording.
If I can help you, call me.
You've got to learn your instrument. Then, you practice, practice, practice. And then, when you finally get up there on the bandstand, forget all that and just wail.
I'm a professional pianist and music educator in West Toronto Ontario. I'm also a devoted percussionist and drum teacher.