My best weapon against unmatched seams is elmers washable glue stick. Glue the seams in place, let the glue dry, and then sew the two butting seams together. Of course, if you use this method, you have to wash the finished quilt to get the glue out.
I have seen people use the very fine straight pins to pin them in place, and that works well for them. But the pins are too darned small for me to pick up these days, so that technique is of no use to me.
And there are those times when nothing I do works. That's when I put those naughty patches in time out and let them rest until they are ready to behave. It's amazing how often that convinces the seams to match up!