I have a few recommendations for you to double-check if you are having trouble getting your seams to line up. Press and starch fabric before sewing and cutting. Many times your fabric will come from the store with crinkles and wrinkles. (Especially if you are working with fat quarters or already cut fabric that has sat on a shelf for several years.) If you cut your shapes before pressing, you may find your edges may be off on one side or the other. Pre-pressing and starching (if needed) will help with this. Make sure your cuts are accurate. If your ruler slides just a little bit each time, it can affect how your blocks line up. Don’t forget to check your seam allowance before starting to sew! Every time I start a project, I line my needle up using a seam allowance ruler. I recommend this quarter-inch foot with the guide. (Just choose one that fits your machine.) Once I have made the adjustments to my needle, the guide helps keep all my seams perfectly aligned.   Squaring up your blocks: Do not skip the step of squaring up your blocks! If your seams are off, even by a millimeter, this will affect how your blocks will line up. (There are special rulers designed for squaring up blocks, but if you are just getting started, a large square ruler will work.) Nesting your seams. Nesting seams means aligning the seams of each block in a row, so they line up almost like a puzzle piece. Nesting the seams can also help line up squares that might be just a tiny bit off as you can fold the edges in one direction or the other for the perfect alignment.