As far as I remember, vectoring is quite good and primary runway is 05 with ILS. NDB approach is used only when ILS is unavailable. When southwesterly winds prevail, ceiling is seldom so low that circling is necessary, more often it's visual left hand circuit to 23. If you're coming from north and 23 is in use Zagreb ACC will direct you to SPL VOR (roughly downwind). Split APP will gradually descend you to 3000 ft and clear you for visual after you report field in sight. On A320 I used to fly at minimum clean and started configuring as I crossed the ridge north of the airport. Downwind was flown with half flaps and gear down. You can use circle-to-land fixes to help you maintain track and start turn at proper place. Despite the looks, there's plenty of room to line up nicely, but not enough to correct if you overshoot the centerline.
Runway is quite undulating, with prominent hump in the middle of 05TDZ and sloping down towards the 23 threshold.
Bring some holding fuel with you if you can. On a couple of occasions last year, arriving traffic was directed to hold for a couple of minute till the parking space became available. The worst part is maneuvering around the too small apron, especially on summer Saturdays. Taxi slowly and when in doubt, stop and ask the marshaller (via tower) to check wingtip clearance. Last year there was wingtip to stabilizer taran between Tu-204 and A320.
Be careful when taxiing out from stands by the terminal not to jet-blast the building. Tight turn with engines at idle is quite difficult trick but it's the only way to play. Also smaller aeroplanes can taxi out from position at eastern corner of the apron, by the fire station, but pushback from it is compulsory for anything bigger than 737.
Cheers, C.