One "gothca" that's often seen in outdoor pictures that are composited is a mismatch of shadow directions. By paying attention to details, such as the shadows, a merged image can be made to be believable. It doesn't take much to figure out, based on the subject of this post, that the picture here is a result of compositing. If you guessed that the truck was put in over the image of the barn you'd only be half way home. The grass in front of the bumper was also added.Take a look at the shadow cast by the eave of the barn. It's fairly easy to see the sunlight coming in from high left. Look at the shadow cast by the headlight of the truck on the fender. Again, high left. If you're really into nitpicking you'll see a very slight discrepancy between the angles of the shadows. The light on the truck comes from a little bit more toward the front compared to the light on the barn.
The barn is in Sherman Connecticut, the truck was in an antique restorer's parking lot in Arundle, Maine. The tall grass in the foreground is from almost anywhere. It's a good idea to take shots of ordinary things that can serve as components of a final image. To get the grass to appear to be in front of the bumper a simple mask was used, A very small brush, making random upward strokes from bottom to top, was used to create the overlaying grass.
One thing to remember, as you play with compositing multiple images, is it has to look real to be convincing. Mismatched shadows have tripped up more than one final image.