it's about as simple as it looks, really.
Two important things to remember is to always set the iron on its backend, so the metal press side isn't on the board or shirt if you aren't going to be using it for a moment, and to always make sure it has water in it and that you keep it moving, even if it's pretty slowly.
Nothing sucks more than having an iron shaped hole in one of your favorite shirts. Never trust your brother to do the ironing :-\
Edit: Oh, a suit? I's probably take that to a dry cleaner. Sometimes those are made of more complex fabrics that are more delicate that your average cotton button-up.
If nothing seems to be happening, then you need to make sure the iron is hot and that it has plenty of water in it. It's the steam that usually does the work. There should be a little button to shoot a little bit of water down as your are ironing, just hit that a little bit.
Move it slowly back and forth over a large area of the shirt, if you rush it, it won't get time to heat up, but if you go too slow you will fry your shirt.