Starting a tenure-track position is a little like going through puberty again: it's scary and exciting to become entirely independent. Depending on the field, people may have gone through one or more postdocs prior to getting a tenure track position, and some have had a fair bit of experience in securing their own funding and governing their own work, so some aspects of a tenure-track position are not new to them. However, I don't think anyone can fully prepare you for what type of havoc the simultaneous pile-on of teaching, grant writing, student and staff recruitment, and service wreaks in your life. Sort of like no one can prepare you for how it is to have your first kid, only sans poop.
The first year is pretty brutal, as all the courses one teaches are new and preparing for them takes a lot of time. And then there is grant writing -- I wrote over a dozen grants my first year, some on my own, some with colleagues. I remember being entirely miserable after my 1st semester, because between teaching, grant writing, service (albeit little), and housework, I was completely exhausted and had no time to do research, which is what really recharges me. So in my second semester I dramatically increased the number of instances I said "no" to offers of grant co-PI-ships and nonessential service, carved out some solid blocks of time to devote to writing papers, and I reached the end of my 1st year feeling much more upbeat.
Tenure track is a stressful period in which one learns to teach, advise students, write proposals to raise grant money, and get along with the colleagues, program managers, and collaborators. One's career actually can go astray many ways; the home department will usually want to protect its investment and help one achieve tenure. During tenure track, a faculty will typically receive annual evaluations, which may or may not always be in writing and may or may not always be detailed enough to be useful. In my first few years, I'd get these vague single-paragraph evaluations that neither praised nor criticized, but the department switched to longer, more detailed evaluations around my mid-tenure-track, and these were quite useful as they listed specific things the department thought about my research, teaching, and service to date.
A mechanism that is implemented some places is to assign a mentoring committee to a faculty on tenure track. These can consist of one or two faculty who are supposed to be the first point of contact for tenure track faculty when questions regarding teaching, research, or service arise. The committee may be required to meet with the assistant professor to go over the progress report, with or without the department chair. The two faculty in my mentoring committee were well-intentioned but I never felt particularly free to ask them for advice, so while they certainly didn't hurt my case I don't think they had as much of a positive effect as they could have, had the lines of communication been more open. I also has an outside-of-department senior female mentor assigned through a female mentoring program, and while she was a wonderful person, I felt that she certainly had better things to do than advise me, so we were in touch quite rarely. In general, all my formally or semi-formally assigned faculty mentors were nice and collegial people but not too available, so I avoided bothering them.
At the very beginning of my tenure track, I asked my former advisor for input on all things academic. But that subsided quickly, and I would say that the most and the best advice on anything academia-related I got from my collaborators. They are the people I trust and the collaboration makes the lines of communication open. While these people never got service credit for answering my inquiries (my formal mentoring committee did get service credit for it), I wish they had somehow been compensated for the time and effort. But I think this is a case of pay-it-forward: you give back by trying to help other junior faculty, so this blog is a bit of me paying my debt forward.
Anecdotally, I know that in some big research schools people are left to sink or swim, and almost no written, unambiguous feedback is given to them on how they are progressing towards tenure – sometimes not until the 3rd year review and sometimes not even then. The lack of feedback just makes a difficult journey even more stressful. I recommend finding out early what the university-mandated and department-mandated types of feedback are, and if there is any type of mentorship you have the right to I advise that you try to have it materialize. Ensure you get all the feedback that you have the right to (and then some), and do so early on.
I am curious to hear how prevalently mentoring committees are assigned in science and engineering departments to oversee a young faculty's career development, and, if assigned, how useful/successful they are in helping the candidate and making the evaluation process less stressful and more transparent.