[roenxi]

I refer to Fundamentals of Queueing Theory by Gross, Shortle, Thompson & Harris.

Although Wikipedia is enough. As far as insights go the topic is relatively simple, it is just bad practice to be re-deriving the first 100 pages of an intro-to-queueing textbook in an emergency.

80% of the time it is enough to assume the process is an M/M/1 queue or consider how the queue would perform relative to an M/M/1 queue. M/M/1 queues are the analog to fitting a straight line, simple & technically incorrect. It is good to move through that part of the day without thinking.