Ed,
It depends on the following:-
1) Is it open plan (already partialy answered)
2) Do the rooms have walls thick or thin?
3) Do the rooms have thick or thin doors?
4) Do these rooms have glass walls or doors, if so how thick?
5) How much coverage of floor space are you looking for?
6) What speed/office?
7) Do you plan to have more than one SSID (i.e provide internal & guest access?)
8) How much do you have to spend?
9) Do you want visible AP's or Hidden?
10) Does the office have a lowered ceiling
11) Do you plan to roll out wireless in other locations?
12) What is your cable mode speed?
13) What LAN infrastructure are you running?