1) There's an NTU sub-forum.
2) Depending on the camps(e.g. faculty/CCA/hall camps), you can apply with friends or go on your own (or sign your friend up). Allocation of OG might not be to your favour either. Acceptance to the popular camps is not definite either
3) There will be a package sent to you about the orientation camps, sometime in june (I think). It will let you know more about the camps, including registration procedure.
Note: If you are just going to stick to your own group of friends for the camp, you might as well not go for the camp...
In any case, just go enjoy your free time now and upload more pics onto facebook.