Madtoonfan,
The viewing area was recently opened up again to its previous size...it gives a grandstand view of the main apron, with a clear view of R07-R25. If you are leaving the airport, there is a lay-by on the main road towards Templepatrick which a/c arriving on 25 pass over at about 300ft. It is frequented by local spotters and the police etc. will not be concerned about you.
Scheduled services are nearly all 737 (bar the MyTravelLite A320s from BHX), while at this time of year you can see a lot of charter airbuses. AirTransat bring in the Tristar from Toronto, and there are a number of wide-bodies from Florida also.
Occasionally, you'll get a good view of a Hercules into RAF Aldergrove.
Good hunting.