I press every seam open that I possibly can - within blocks and rows. I like the flatter block/quilt.
I use a variation of Prism's method when joining blocks. I place the pin straight up/down through the intersection but not into the ironing board. I hold that pin steady then place pins normally through the 2 pieces of fabric on either side of that up/down pin. I do not glue but find that the 2 pins on either side of the seam hold everything in place quite well. I also sew over pins (yes, bad girl that I am) and find I don't have shifting issues.