I normally pin 1 -2 inches apart after I get my initial two sides pinned. Running your hands from the pinned edges can get your quilt to "stretch" if you are a little undersized. If my quilt is a little too long in either direction (not usually my problem) I will pin the corners and then ease the excess along the total distance of the edge.
As a last check I use a carpenters square to verify that I have the edges pinned along a straight line and 90 degrees to each other.
On our video page is a short video of the process with the same photos, but text over each step. Let me know if you use my technique or if you have a better way.