The beauty of tarps is that you can pitch any of them in a jiffy using several traditional rigging techniques. The examples described below work well with rectangular and parabolic models, and require only a few feet of guyline, several trees or rocks, and, just maybe, a little improvisation.
Run cord between two trees and flip the tarp over it lengthwise. The lower the cord, the better your weather protection. Guy the sides out to the ground at a gentle angle.
Plus: Center line doubles as clothesline for drying socks.
Minus: Extra cord adds a bit of weight.
Lay the tarp perpendicular to the wind, and stake the long, windward side low to the ground. Guy the opposite side, at least 4 feet off the ground, to trees.
Plus: Effective protection against wind-driven rain and snow.
Minus: Better hope the wind doesn't shift.
Lay the tarp perpendicular to the wind, and unfurl your bedroll on the leeward half. Fold the windward half back over your bag and guy it at an angle to prevent runoff, giving yourself at least 6 inches of clearance.
Plus: Protects your bag from wet ground.
Minus: No room for a hiking partner.