Make sure the angle you are pulling on the tarp is good. The right angle, usually around 45 degrees to the ground (straight out from the corner of the tarp) will give a more taut pitch. If you see wrinkles in your tarp, this is a good sign you need to stake it at another angle.
Is that too much to ask? Girls with frikkin' lasers on their heads?
The hanger formly known as "hammock engineer".