If you need circle paths use the create>nurbs primitives>Circle to attatch a camara to a circle.

It will time the path to make the camara go the whole length of the curve in the given frames. so if you have a circle with 24 frames it will go from 0 degrees to 360 degrees in 24 frames, so at 12 frames it will be on the 180degree mark. If you had 48 frames. it would go from 0-360 in 48 frames. so the 24th frame would be on 180, the 12th on 90.

I hope that helps. some. If you want to view from the camara you made and put there. Click it and on the top of the panel your in, select panels>View through selected.

Good luck(sorry if there might be some inconsistencies, i just learned this yesterday)