Well, Pat, if you insist on dragging out a soap box for me, I guess I have to climb up on it! *grin*
First off, you need a HOT iron. Unless you have a really old iron made before "they" decided to protect us from ourselves, turn it all the way up. Doesn't matter where they claim the cotton setting is, turn it up. Unless you're scorching the fabric within 30 seconds, it's okay.
Second, I always use steam. Yes, I know quilt teachers sing the praises of a dry iron. IM(NS)HO, that's because newbies can use steam to really stretch that block WAY out of shape. But none of us here would abuse our fabric like that, so use that steam. If your iron doesn't give off a healthy amount of steam (or if the fabric is really stubborn), have a spray bottle next to the iron to give the fabric a quick squirt. Make steam your friend. (FWIW, if any of you are worried about stretching the block, the ironing board police will NOT arrest you if you take a *permanent* fine tip marker and your rulers and draw a couple of straight lines at right angles on your board. Now that I have the lines on my board, I never use starch anymore because I just don't need it.)
Setting the seam (do we all know what I mean by this? If not, please ask!) really is important. I'm all for skipping unneeded steps, but this does make a difference. Not sure why, but my pressing is always better when I've set that seam first.
Whether you press open as I do, or press to one side, make sure the seam is all the way open. At classes I often see people plonk their iron straight down, no doubt as they were taught in a beginners class, again to avoid stretching. Unfortunately, that sets any little folds into the seam. If you use your iron to *gently* move the excess fabric away from the seam as you press, the pressing will look better and your pieces will end up the size they are supposed to be. As you get more comfortable with this technique, you can press just about as fast as the plonkers.
Lastly, pressing is not something to rush though to get back to piecing. I used to be guilty of that, and the results showed it. Now I have a more Zen approach. I move the iron as slowly as it takes to get a good press. You can have the hottest iron in the world and the best technique, but if you try to press that seam in 1/10th of a second, the fabric just can't get hot enough for the iron to have a bit of effect on it. Moving just a bit slower doesn't take much longer, but makes the end result so much better that it's worth it.