You should take bus 191
in the direction of Schiphol Zuidoost, or busline 198
in the direction of Uithoorn/Aalsmeer. You should get of at busstop Aalsmeerderweg
From there it is another 10 or 15 minutes walk into the Aalsmeerderweg, which will be on your left when looking in the driving direction of the bus. This road runs parallel with the runway and if you walk to the end you will find the spotters site.
Another option here is to stay at the busstop and shoot photos of planes in the final approach for 06/24. You could also stand here when 06/24 is used for take-offs, but most of the planes will then be too high for good photos.
You can find more detailed instructions and maps at my site:
[Edited 2004-12-12 02:08:32]