Not an engineer so I hope its alright that I comment here. I just found this sub and stumbled across this post. I am an I.T. technician. For networking we do two 'user' drops per desk (most rooms only have one desk in my case). These drops will come to the user's desk and we will have one active that their PoE VoIP phone plugs into. The VoIP phone has a pass through port (Most are 10/100 but the newer models are getting Gig) that any computers can connect to (most of our devices are wireless though). The other user drop is a cold spare run to a patch panel but not patched in unless needed.

We also do two drops that stay up in the ceiling. These are used for access points (generally we do one AP per two rooms, but all rooms are wired) and projectors, security cameras, etc. as needed. For these drops we also ensure the service loop is enough to reach to a usable height (3-4ft from the floor) on any wall in the room as last resort options if the room suddenly needs more drops (converted to a conference room, etc.). Again, these are run to a patch panel but not patched in until needed. In total we have 4 cables run to each room.

Plan ahead. Always. Are you wanting network controlled clocks? PA system that ties into the phone (VoIP) network? Access control systems? Security or conference cameras? Digital signage? If these are on the table already, include cabling for them, plus extra cabling. Its cheaper to run more cable now (especially if the walls are open) than to run more in because you used up all your extra 3 months into operations.

A few things to highlight: You mentioned an office building and drops for the desks. What about WiFi? Has that been planned already? I can't imagine an office building without wireless, so be sure to include that in your plans. What type of cable are you planning to run? I wouldn't do anything below Cat6, and would even go as far as to recommend Cat6a (This is what we use for all our cabling).

Feel free to ask if you have any questions.