The best thing band members can tell their instructor is they practice in their spare time. Directors love to hear that their members are taking it upon themselves to improve away from organized activities. If they aren't already done so, these members could become future candidates for drum majors or section captains.
Practice makes perfect, so as director you should encourage your ensemble to practice whenever they can. Let them know it'll be more valuable to their performance to forgo watching TV and instead hone their musical abilities.
Here are two tips that can help your members become better musicians:
1. Use a metronome
A metronome is a great way for musicians to help maintain an established tempo and learn complex music notes. It's a practice tool that creates a stable beat and helps members play more accurately. A metronome helps musicians get their timing down and play more evenly. This ensures they aren't getting ahead or dropping behind others during a performance. If your program supports it, think about purchasing one for each member of the band.
2. Establish study groups
Study groups aren't only for math, history and the social sciences! Musicians can get in on the fun too. Encourage each group within the ensemble to get together on the weekend at least once or twice a month, even during the season. By practicing together, they'll become more unified and thus, more fluid when performing live. As a director, this will also make teaching easier because you won't have to teach many new concepts from scratch. They may have already self-taught each other in their groups.