The first thing to decide (which I suspect you already know) is to decide what kind of campus the college has.
There's Rural, Urban, and Suburban.
Rural campuses tend to be all contained in a large plot of land with maybe 1 or 2 roads in/out of college. For example, my wife's college was on a mountain. There was 1 road that went downhill, and a footpath that went to the top of the mountain. They also tend to have lots of green-space and buildings tend to have some lawn around them. Unfortunately, if you want to get away from the campus for any reason, you either need a car or some really good walking shoes. As a result rural campuses tend to have more businesses/entertainment options that are run/endorsed by the school.
Urban campuses tend to be completely integrated into the city's grid of streets. There will be tons of ways on/off the campus. The buildings also tend to be very densely packed. They also tend to be taller buildings than on a rural campus. Fortunately, if you need a break from studies, you only need a bus-pass. As a result, the college will usually choose to not include restaurants/theaters/etc. that are run/endorsed by the college.
Suburban campuses are sort-of half-way between the two. Some will have lots of roads on/off the campus, others will have one or two roads in/out. Some will have greenspace, others will be densely packed. The local suburban university has 5 roads into it, and the "outer ring" is densely trafficked. You end up driving onto the campus and parking in the garage, then walking between classes. The central area is very similar to a rural campus, but the "outer" part is very urban. As for amenities? THere's a shopping mall across a major thoroughfare from the campus, so it's pretty urban in that regard.
Another major decision that you need to know is whether the college will be a residency style campus or a commuter campus. My local Suburban campus is about 80% commuter, so there aren't many dorms. Rural campuses tend to have a much higher percentage of residential students, but that is also partly because urban schools all have privately owned apartement buildings nearby (and expect students to rent apartments after their Freshman/Sophomore year).
As for building placement, I would start in the middle with a common area for students to hang out/play sports/study, then build out from there. As @CatLord said, some campuses are very haphazard. Others are very organized (residential halls on one side of the green, class buildings on the other). Others started out organized, then built outwards as they needed a new building.
Finally, if this is an NCAA (or foreign equivalent) school, don't forget areas where the sports teams can practice/train/play.