Here's the inspiration image:
Here's a micro-tutorial on blending techniques I used for this page.
There are some interesting attributes you can add to a layer in Photoshop's Layer Styles menu. Here, I played with the Underlying Layer blending to make the chalk graffiti look more realistic on the corrugated wall. For the white frame, I slid the black marker to the right some, and the white marker to the left, until I was happy with the look. I repeated the same technique on the splatters and other chalk elements. This is a really helpful blending technique with text on a page, as well, particularly for art journaling style pages.
Here's an example of using it with text, and I took it just a step further.
One more thing to note, when you use these blend modes, you see a slightly different icon in your Layers Palette, two intersecting boxes. This indicates you are using advanced blending options.
What's a technique that you use and think is sometimes overlooked?