This is a panel from the "Prince Valiant" comic book that was available on Free Comic Book Day. It caught my eye because it's a good example of the way I like to use detail in drawing.
There's a good balance of empty areas and areas with detail, and I think the contrast makes for a pleasing drawing (contrast is always a useful method for creating a good illustration). And the artist also was very smart about where the detail was placed. Detail will always draw the eye in and encourage it to linger in an area, while the eye tends to flow through big empty areas quickly and easily. And the story content of the panel is that the pirates on the boat are looking at the town in the distance longingly because they want to plunder it, but their captain won't allow them to. So the artist wants to call attention to both the men on the ship and the town in the distance. To get the viewer to look in the right places, detail is used for the hills above the town, and for the ocean near the men on the ship. In both cases, the detail isn't exactly on the focal points, but instead, very near to them. So you don't always have to put the detail on the exact focal point. Somewhere nearby can do the job just as well.
And in the areas of the picture that the artist doesn't want you to dwell on--like the rocks in the ocean, or the hills on the right side of the composition--the artist uses detail sparingly or not at all.
I have met people that have said that they feel the more detail a drawing has, the better a drawing it is. That's certainly a valid opinion. And there are some comic book artists that tend to use detail on every area equally when they draw panels. That's a stylistic choice, and there's nothing wrong with doing that, but personally I like it when an artist controls my eye and leads it to where he wants it to go, and doesn't confuse me about what is supposed to be important and what isn't necessary to focus on. I think the best artists are storytellers that use every trick they have to help tell the story in the clearest and strongest way possible. So keep in mind that detail can help organize your drawings and attract the viewer's eye where you want it to go, and use that method to help tell the story you're trying to tell.