Yes I set the seam and then press it open...of course noticing I didn't say the word 'iron'.
SET - put iron on fabric pieces as they were sewn (think about ironing a shirt - you'd smooth it out before really ironing it)
PRESS OPEN - open the seam and gently press the iron into the seam - don't iron it.
I think each seam looks pretty when pressed.
and I think it makes a difference in my blocks.