Technically you are meant to request the noggins during the electrical appointment.
However, I spoke to my SM and he just put them in where i wanted them. All they want is locations and the height that you need.
Getting it done through the SM is better anyway as its no cost, they charge you if you do it through electricals.
Mind you it depends on the SM, ours is quite good and didn't give a hoot about putting them in.
We forgot this but you may also consider putting noggins in where you will have wall hung cabinets, eg a tv entertainment unit or a cabinet for your IT switches and routers.
Metricon Liberty 45, Ryde NSW
http://forum.homeone.com.au/viewtopic.php?t=82846