Best bet would be the nature reserve.
The entrance to the Nature reserve is on the Rysmierbult road.
In the reserve, carry on with the dirt road just about all the way around the dam. At some stage you will find a patch of huge blue-gums right on the edge of the water. Right in front of the trees there are a fairly large area that is reed free (compared to the surroundings). You can park there. Right in front you have a nice gravel bed that that gives you bit of a weed free patch. To the left there are breaks in the reeds here and there, with one or two nice little "bays" in the reeds. These are prime spots! To the right of the trees and gravel bed, you will also find long lines of reeds with openings in between. These are also great spots, but calls for stealth-mode wading just past the reed-line.
Like the guys mentioned, the water is extremely clear so you have to be extremely stealthy, and go as light as possible, but then again not to light as Boskop has a lot of structure and cover, and if you give too much rope, you will end up busted in the weed-beds.
The main bait-fish in the dam is "vleikurpers" or Banded tilapia (Tilapia sparrmanii), of which there are absolutely millions. You also get mosquitofish (Gambusia affinis), carp, mudfish, yellowfish and barbel.
It is a tough dam to fish, but extremely rewarding!
Good luck!!!