If I dont pin each intersection, my seams are off. That is really the ONLY time I pin. Good luck!

Another way to get the seams to match is to nest them together like normal, then pin ACROSS the seam. Let's see if I can explain it, lol Nest the seams, come down JUST PAST the 1/4 mark, enter your pin IMMEDIATELY ON the right of the seam and come up IMMEDIATELY to the left, using only the tip of the pin to hold it in place, open it up and check if it's straight, sew at the 1/4 inch. As you sew over the seam, your pin will be under the left side of the foot. As you go over the seam one or two stitches, pull your pin out. Try it, it works for me. Syl

Thank you to everyone you commented! I have a lot of ideas to try!

I glue baste when I really need accurate matching. I put a dot of glue on the intersections. Then, I measure each piece as I finish it and measure again when I sew pieces together.

I saw Mary Ellen Hopkins several years ago on Simply Quilts and she said that you should never sew long strips together because you are more apt to get things wonky. She suggested to make them into large squares then sew the large squares together. That way you only had one or two long seams to sew. I do this whenever possible.

I generally pin on both sides of the intersection, particularly if there seems to be a bit of unevenness. I try to press the seams in opposite directions between rows so they nest. If the pieces are large, I generally pin more than just the intersections. AND YES! you will get better with practice.

It is probably that stinker "the scant 1/4 inch." If you sew your seam the same size, every time, your seam will match. I measured a scant 1/4 inch and taped one of those plactic cards (like a credit card) in place so my seams are the same every time.

When I discovered fork pins, they made all the difference for me. The end is in a "U" and you place the pin straddling each side of the seam. That way the fabric cannot shift. Be careful, though -- these are very sharp pins!

That Elmer's is wonderful. I use it also. I also pin my seams when they need to match. I make sure to stick the needle in right on the seam and check the backside of the other fabric. If the needle did not come out exactly on a seam them I repin until it does. That is the best way I've found. Then don't remove the needle until you are right at the place as close as you can get.

Get the video by Sally Collins on PRECISION PIECING. All her suggestions improved my piecing tremendously and I find I go back and review occasionally as bad habits try to creep back in.

Accurate cutting, and 1/4 seams, and pressing seams in different directions will give you a perfect seam.