Welcome to the board from Oregon!
Okay, first ~ quilters DO NOT iron, they press. I usually do what is called 'set the seam' which is I run my iron over the seam that I just sewed.
http://www.youtube.com/watch?v=9sw5QJr2mGw Second ~ different patterns will suggest which direction you need to press to have the blocks 'meld' better. The old school was to always press to the dark, which is a general rule to have.
There are many you tube sites that will help with all sorts of quilting questions. Good luck