Case in point:
So let's talk font bling.
I use Photoshop, so I'm most familiar with how to treat text in that program. I'll refer to how to do these effects in Photoshop, but I assume other equivalent programs can do similar things.
In Photoshop, right click on the text layer you want to enhance. Right under Layer Properties, you'll see Blending Options. Choose that and a pop up menu will appear. In that menu, you'll find most of the following options.
Here's plain black text (Garamond Pro) on a medium dark colored background. We'll gradually build up this text to experiment with various effects.
If you learn to do nothing else, learn to add a drop shadow to your text. The drop shadow alone can often make an amateur title look pro. Learn it, love it, use it.
Bevel and Emboss are what gives your text that 3D "pop." Photoshop automatically adds the highlights to give these letters their depth. You can adjust the angle, but usually the out-of-the-box bevel and emboss looks fine. Again, just adding this, plus drop shadow, gives your text the self-respect it needs to hold its head high in the world of book covers.
You can rough up your text a bit by adding Texture. This is easy to over-do, and too much Texture can make a font impossible to read, so consider subduing the effect by lessening the opacity or choosing a subtle weave from the Texture menu.
Inner glow can give a spooky or magical look to text. Not shown very well in this example. It works better with some fonts than others.
Another nice effect is Gradient. It's important that the color scheme for your Gradient works with the rest of the cover. Also, consider the light source in the images on the cover (where is light "coming from" in the picture) when you decide which part of the lettering will be lighter and which darker.
The Stroke around the letters is one of the most abused of all effects. You'll often see amateur covers with the text outlined in bright red, despite the lack of bright red in the rest of the cover, or any other justification for such garishness. Why? That's the color it comes set on. This abuse means that you should think once, twice, three times before using Stroke. However, Stroke doesn't have to be bright red...and usually shouldn't be.
Outer Glow is probably the effect I use most often, after Drop Shadow and Bevel and Emboss. It helps the letters stand out. You can make it brighter for a "magical" look, or softer for a more subliminal effect.
This is the same as above, except with a white, light airbrush under the title instead of a dark one.