You'll expect and anticipate change. Inevitably, you'll want to know whether, and how, your own role and routine will be affected. And if you're sensible and experienced, you will acknow-ledge that not everything that happens will be welcome - though you'll hope that all will eventually work to the good of the children.
Over the years, I've seen that first September, and the weeks that follow - as parent, teacher, governor, consultant, friend, mentor - and of course, as a new head.
Gradually, I've realised that although it's a time of many challenges, the one that overrides all others is simply that of staying focused on the core business of teaching and learning in the classroom. That's what the new head needs and wants to do - in some cases as a matter of great urgency - and it's also what teachers, support staff and parents expect.
Worryingly, though, it's also what new heads find most difficult - and that's something colleagues need to remember when they find that a lesson observation is cancelled, because their head is once again in a meeting with someone from the education office.
Two different headship stories bear this out. One is in a research paper on the website of the National College for School Leadership. The First 100 Days, by NCSL research associate Patricia Brown, follows the newly- appointed head of a primary school in special measures as she strives to turn things round.
It's a striking record not only of courage and professionalism, but also of the enormous frustration that comes with endless distractions from the main priority. For "Angela" - names in the report are fictitious - part of the problem was tackling a legacy of organisational muddle (there had been a succession of temporary heads), which conspired to draw her, repeatedly, from the classroom.
Patricia Brown writes: "A feature of this failing school was that it had few effective management systems. The task (of creating them) was essential but time-consuming and a distraction from other key concerns, such as monitoring teaching in the classroom."
The danger here, Ms Brown points out, is the implied message to staff that teaching is not the main priority. And distraction is not only there in troubled schools, as I found when I talked to a primary head approaching the end of her first year in an ostensibly much less challenging post.
"Liz" (let's call her that) took over a school that had done well in two Ofsted inspections, led by a long-serving larger than life headteacher regarded with affection by the whole community. It might have been reasonable for Liz to assume that teaching and learning were doing fine and could be left alone for a while, but that is not her way, nor should it be.
She needed to be out of the shadow of her predecessor, and part of that meant, as a priority, building her own picture of what was happening in the classrooms.
"The first term is when you should be in there, learning children's names and getting to know staff and how they work," she says. "I had the previous head's observation reports but I wanted to make my own judgements."
She was always battling other demands on her time. There was the budget, for instance - marching steadily on, powered by decisions made before she arrived.
"Inevitably, you're picking up a budget that already has a term's spending commitments on it," says Liz. "That's really difficult, as you don't have the deep understanding of it, and of the decisions that led to it.
Governors were anxious to get on and get things done, but I didn't want to spend money until I was sure what was happening."
There was a building project to deal with, too - and you can ask any head how that becomes a device for eating up precious time.
Particularly frustrating, however, were the constant demands for attention from officers and administrators in the local authority - the very people, you might think, who would understand the head's need to focus on priorities.
"The advisers are excellent," says Liz. "It's the others who walk through the door all wanting a piece of you - from health and safety, buildings, child protection. Each one thinks their issue is the main thing, and they don't realise they're part of the big picture. I could have been out of school 20 days in the first term on induction sessions with various departments."
It's time, surely, for leaders of authorities to catch up on this, and make sure all departments understand that what they are there for is to support their heads as they strive to concentrate on what's happening in their classrooms.
Despite everything, though, Liz, like most new heads, is enjoying the job, relishing the buzz and the challenge. And an important driver of that positive feeling is the support from her staffroom.
HOW YOU CAN HELP YOUR NEW HEAD
Be visibly welcoming. Use the word itself, smile, offer a hand. "Staff made me feel they wanted me here," says new headteacher Liz. "It helped that I'd made it clear from my first visit that this was the job I wanted."
Be understanding when decisions that affect you are slow to emerge. "We all knew I had staffing decisions to make. But they understood that I needed time to find out what was happening and what needed to be done."
Don't grumble behind closed doors. "If you don't like something, say so,"
says Liz. "If the response isn't what you want, that's a shame, but it's better to have shared your feelings."
Be ready to give advice. "You have the background knowledge of the community and the families."
Keep the head aware of traditions. "There's a time to gently prompt about what normally happens at Christmas, for example, or Divali, and to ask whether it's going to continue."
Above all, be patient. "Both sides just need to wait and see how it pans out. Think of all the times you have found yourself meeting a new class.
That's what it's like to be a new head," says Liz.