When runways 18R, Polderbaan, and 27 or (more commonly) 18C, Zwanenburgbaan, are in use for landings, the most westerly runway, ie 18R, usually gets the traffic from the west (UK/Atlantic) and the other runway the flights from the east. As you say, there are many exceptions, and I'm not sure what the Kenya Aw routing and thus the more likely runway is.
It's similar when 06 and 36R are in use for landing, and when two runways are in use for departures.
I = inbound peak, two landing runways, one departure runway
O = outbound peak, two departure runways, one landing runway
0700 – 0920 LT
0920 – 1040 LT
1040 – 1140 LT
1140 – 1240 LT
1240 – 1400 LT
1400 – 1500 LT
1500 – 1600 LT
1600 – 1820 LT
1820 – 2000 LT
2000 – 2200 LT
As a rule, the aircraft you want will arrive/depart just around the time of a change
Current runway use:
Rwy 27 is bad for noise and typically used in stronger westerly winds.
A380 may land on all five main runways but may not take off from 09 due to a weight restricted viaduct.
Hope that helps.
[Edited 2012-09-12 02:15:21]