"Okay, so we're going to start with a run-through today."

As I've traveled around to work with different bands - be it to pop in for a day of consulting or working long-term and in-depth - I've had many directors ask about what they need to do to improve. 
While there are many various ways we all can improve regularly, one of the simplest and easiest fixes to get your program achieving on a whole new level - points better; placements better - is having a structure to the rehearsal.
Some of the programs where I've seen the biggest need for this are where I stop in and the director says "alright, we're going to start with a run-through."

You're what?!

"Well, I want to see what we need to work on."

Often, I like setting an analogy to other disciplines. So - let's imagine a meeting between a math teacher and the principal.
"What's on your lesson plan for today?"
"Well, we're going to start off with the state test. Then I'll see what they need to learn after that."
"You're doing what now?" Why don't you already know what they need to learn?"

​This is no different than the marching band. How did you performance at the football game last Friday go? What was bad there? Chances are it's still bad today.

Another one that amuses me:
"We need to work on endurance."

Doing an extra run-through of your seven-minute show isn't going help endurance at all. It doesn't work that way. 
​
What DOES help endurance is over-training all the reps, so that muscle memory kicks in when the students start getting tired. As they get tired, their minds focus on being tired, not on performing. If the muscles already know what to do, it takes less mental energy to execute every little detail. 

As the band director, it's your job to think about these things, to be thoughtful in planning out a rehearsal and, most importantly, use every second of time your instructors and your students are committing to your program in the best way possible. 
​In our previous example of the math class, that teacher can probably figure out what they need to accomplish in their class that day and get through it just fine. Writing out a lesson plan lets the teacher put things into a logical order and to plan for a flow of events to teach as efficiently as possible.
The marching band is no different. We often treat it differently because it's an extracurricular (usually) and thus also not subjected to the same kinds of professional standards and observations as curricular classes. But the principles of planning still apply and they have the same positive affect as in the classroom. 

Most bands (admittedly: not all) have a staff. You're paying these folks to be subject-matter-experts to make your students better. If they don't have an opinion about rehearsal goals then they aren't the right person for the job. At the very least, the morning before your rehearsal (if not even the day before your rehearsal), ask your staff what they need to work. Create your own hit list. Come up with all the things that need to get better. How long will each thing take to accomplish? Is it a 10-minute fix? Or is it a 45-minute fix? Do you guard staff and your percussion staff have concerns in the same part of the show? 
Look at the big picture of what your band needs to fix. Prioritize it. See what you can fit into your rehearsal schedule for the next day. Write out a schedule, including the times spent. Get detailed: we're band people, after all - excessive attention to detail is what we do.
I looked back through my tour journal that covered the summers of 2016 to 2019. Every day, we would have a meeting and discuss the priorities for our brass line. I would leave that meeting with details - such as:

• 2:00 to 2:40 - Warm up. Focus on X, Y, Z...
• 2:40 to 2:55 - clean rhythms in measures 4 and 5 of Letter C
• 2:55 to 3:07 - work on intonation at Letter E
• 3:07 to 3:15 - Fix breathing holes at Letter H
• 3:15 - transition
• 3:30 - stadium

This is the level of attention I would put in as a subsection tech. For you, as the band director, make a plan at least this detailed - if not more. 

• ​Allow for solid, adequate warm-up time. The warm-up should be more than just blowing some long tones; it should set the tone of the rehearsal block, get the students focused, and give each section's instructor a chance to address some fundamentals. Never short-change the warm-up.
• Include transition time in your schedule. If you're not thinking about travel time across campus and time to get water, you'll feel like you can never finish your plan.
• Don't over-plan. You have three months; you're not going to fix the whole show in three hours. Take the time to teach two or three things thoroughly with enough reps that it'll stick. If you gloss over it today, you're going to keep glossing over it every day until November.

At the end of the day, as the professional music educator you are, you already know what your band needs. Starting your block with a run-through isn't going to make them better. It takes away 10 to 15 minutes of rehearsal time, which means that's 4 or 5 reps of something that needs work that isn't getting the attention. ​Every minute of rehearsal should carry an obligation to honor the time commitment of all the people on the field: yourself, the staff, the students, and their parents. We always preach to the kids "don't throw away any reps." We, as the teachers, should have the same commitment to planning for those reps.