Lots of interesting suggestions.One not discussed is the thread size. Thread does take up space when the squares of segments in the square are pressed. If there are lots of patches in a square use a finer thread; the sections should be measured before moving on to the next step. As mentioned several times pinning carefully will keep the pieces from skewing as you move down the seam. Remember that the feed dogs always draw the bottom fabric a little bit-that little bit grows alot in a long seam if not carefully controlled. When I join long rows of blocks I use my walking foot rather than a regular foot-just like the process of adding long sashing and border strips. One more thought, when you mark your machine with tape for a consistent 1/4 inch seam be sure to elongate it behind the needle so that it feeds completely through the machine.