Requests to possibly make, in order:
1. Sunset Savanna view. 80% of all savanna view rooms overlook Sunset so request is likely to be granted; Sunset has giraffes and zebras, the smaller Pembe Savanna does not.
2. Room near the Rafiki elevator. It is on north side of the building (lobby faces west) not very far from the lobby, and provides the shortest trip from the building to the pool. Down that elevator to first/parking lot floor gives you a short trip to a gate to the pool.
If instead you would like to be close to the bus station (on the south wing), make that second request room near the Timon elevator, also not very far from the lobby. Down that elevator to second floor (same floor as lobby) leads to a door that provides shortest trip from building to the bus station.
Many suggest requesting close to lobby. That is a good request if you actually get it. The problem is that large numbers make that request including because it is included in requests one can make online when doing online check-in, the building is about 2/3 mile long, and everyone is trying to avoid the forever walks to the lobby, with the result that many have reported not getting that request granted, and, if a location request cannot be granted, they don't try to find something close to what you requested, but instead put you in any available room, which is often one far from the lobby. is
Many also suggest requesting lower floor (second or third floor rather than fourth or fifth). To me either is fine with savanna view -- lower floor gives more direct-on view of animals, while higher floor provides more panoramic view.
Any request should be made through MS via email, chat or phone and can be made as early as when you make the reservation. During online check-in, there is a page that allows one to pick a room location request. Skip that request page during online check-in if you make requests through MS. Using it will wipe out any request made through MS and requests you can make during online check-in are few and at least one of them is completely ridiculous: you can request near an elevator (but cannot, when doing so, give the name of which elevator); there are three sets of elevators stretching along each of the two wings and a close to elevator request, without being able to name which elevator, can be met by putting you in any room in the building.