I recently received an email asking if I would be willing to evaluate a colleague's application for promotion and tenure. We are both at R1 universities in the US. According to the guidelines, I am qualified to serve as an external evaluator even though I am neither tenured nor in a tenure-track position. However, this means that I have limited familiarity with the process.

I am inclined to accept and support the case, but would like to know:

* What is typically involved in such a review? How much reading and writing? Can I expect to do this in a single day?
* What makes a great (great = valuable to the committee) evaluation?