When you are sewing rows together make sure you pin at each seam. The seams should be exactly on top of each other. Then line up the ends. In the instances when you are pinning one triangle on top of another triangle make sure any diagonal seams meeting in the same place line up with each other.
After you get the seams and ends pinned together then you can ease in small amounts of fabric if needed by pinning in between the seams as well. If one square is so much larger than the other in the row that it would create a pleat to try and ease the fabric in, then something is wrong and you'll have to pick out and re-sew somewhere.
