How hard / How to be appointed as a Professor from Assoc. Prof?

Answer 1

The above answer is incorrect.

Tenure track positions begin with assistant professorships, move to associate professorships, and then to full professorships.

The qualifications for promotion from associate to full professor vary from university to university, but generally, another book is expected. I say "another" book because, generally, it took the publication of a well-reviewed book to be promoted to the associate professorship in the first place.

This can also vary by discipline. In the hard sciences, a certain number of articles with first authorship would fulfill the same function as the second book.

One MUST consult the P & T (promotion and tenure) guidelines at one's own university, and within one's own department, in order to get the best information for oneself.

Full professorship at my university requires demonstrable and measurable evidence of:
1) quality teaching and advising
2) quality research and scholarship
3) service to the university and the profession (on the national and/or international level)
4) strong recommendation for promotion to full professor from at least three of four external reviewers, selected by the P & T committee. The reviewers themselves must be full professors at other institutions who are very familiar with the scholarship of the person up for promotion, and must themselves have recognized international scholarly reputations.

Answer 2

I don't think associate prof is tenure track - you'll want to get a job as assistant prof instead; that's usually tenure track.