I don't use steam, but to be honest I have forgotten and pressed with the steam function on and never had any distortion that I could notice. I think I get a crisper flatter result if I press with steam and a little bit of Best Press though. I also keep a bottle of water by my ironing board for wrinkles that won't come out.
The biggest habit that has been helpful to me is pressing not ironing - as many other ladies have mentioned. I generally open seams with my fingers first and use my nail to sort of create a "guide" for pressing. You can also buy a little wooden pressing stick from the craft store for a few bucks...I use that when I'm making something with a lot of seams so I don't have to keep getting up and going to the ironing board. Like this pineapple quilt I'm currently working on, I usually finish the entire block and just use my wooden pressing stick and then take it to the ironing board and press with a little bit of Best Press.