pax' website, has a good section on dryfiring safety.
http://corneredcat.com/TOC.aspx#Practice
Don't neglect safety, dryfire practice is a very good way to have an unintentional discharge unless you're very careful. Also make sure that your firearm will tolerate dryfiring--most will but some do not.
During dryfiring practice you align the sights, aim at a target and squeeze the trigger. The goal is to watch the front sight and have the sights stay aligned and properly aimed at the target during the entire process until the gun dryfires.
You can try the pen & wall method or attempt to balance a coin on the gun during the process, but it's been my experience that a shooter can tell by looking if the sights are moving or not without resorting to any special techniques.
You can experiment with different finger placement on the trigger to see if that helps and you may also find that adjusting your grip slightly can help. Even when there's no movement visible, dryfiring is training your brain that it doesn't need to associate the process of trigger pulling with loud noises and recoil and it's also teaching you to watch the front sight and also giving you muscle memory relating to how you hold and aim your pistol.
About the only thing dryfiring won't teach you is recoil control, but if you use a proper grip/stance it can even help with that to at least some extent by ingraining the proper grip/stance into your muscle memory.
One last point. You're training your body and mind when you dryfire. It's obviously preferable to train them correctly so make sure you're doing things (grip/stance/sight focus/etc./safe gunhandling) right so you're not ingraining bad habits.