Thanks for the tips. Though I have been able to find somewhat advanced info about flash online, it's actually hard to find basic information (even in the manual). I suppose much of this will be answered by practice, but here are some of my immediate questions:

I almost always shoot in aperture priority mode. Do I continue to choose my aperture (and ISO) for a given scene in the same way I would without the flash, or does use of the flash change everything?

What happens to the 1/100 rule when using a flash?

I know I'm supposed to bounce the flash off a wall or ceiling if it's close and white; otherwise, should I always point the flash head directly at the subject?

The flash gives my a zoom readout (e.g. 50mm) when the head is pointed at the subject, but otherwise reads only -- mm. Is it functioning properly?

In what situations should I prefer the naked flash, the Sto-fen or the Lightsphere over one another? I've been assuming I will use some type of diffusion most of the time, unless it's simply not producing enough light for the setting (e.g., a poorly lit room).

I know that's a lot of questions, but I'm a lot confused. Any help is much appreciated.