Haven't camped there myself, though it might be quite a busy site being next to the major routes up and down from Helvelyn/catstyecam. That does mean that the footpaths are pretty obvious - navigating down to Glenridding shouldn't be a problem (have a look on Google earth / other aerial views!
Looking at the map (and from memory) there is very little flat land around there - the contours of the cwm slope straight down into the lake - so finding even a small spot to place a tent might be difficult. Around the lake outflow looks most likely, but the flattest area (S of the outflow) looks like it might be boggy with that small pool and there are also a lot of rocky areas.
Given how busy it could be, and the limited camping sites, I would always be looking around for alternative spots in case there's no room at the lake.
Near the sheepfolds at 358168 would look a good alternative to me - Sheepfolds are usually flat, away from boggy areas and often there is room to pitch inside the fold which gets you a lot of shelter if it's windy.
Near the abandoned dam at Keppel cove might also be a possibility?
Edited: 30/07/2012 at 09:57