I have a OES Mac Cat. My usual ground pitch is a flying diamond, one pole with most of the D rings staked to the ground. You can pitch with the open end close to a rock overhang or tree to obtain some protection from rain. Foot end can be pitched off the ground slightly for ventilation.

I would try to get a tighter pitch - in wind the sag in the tarp will keep you awake with the flapping.

Sgt Rock has good pictures, so I don't have to replicate.

http://hikinghq.net/gear/tarp.html