Be careful if you're using directional prints - I just went through this with a bunch of prints that were not only one way, but also varying width stripes (what a nightmare). You do not put them top edge together. Pin and open before sewing so you can see how they line up - you will usually need to put the upper edge of the top square to the right o left side of the bottom square.
Hard to explain, but if you pin and "peek" you will see how they come out before sewing them.
K Cama