I was thinking of this when I was practicing this morning and of a common issue I encounter, as I do also in my community band... holding a note for its full duration. A half note is a half note, not a dotted quarter. A whole note is a whole note, not a dotted half. When you practice, make sure you hold those notes as long as you're supposed to, and it will carry over to your ensemble playing as well.
After my section mates find me dangling in the wind holding a note its full duration, they get the hint and start doing it themselves, though I admit sometimes I have to cut a note short because they just don't figure it out some days.