A quick way to get correct perspective when applying a graphic to a flat element of a scene, such as a wall graphic or decal on the side of a truck.
Here's our truck - now we want to put our logo on it.
Of course, we can just paste our logo into the scene and use perspective transform, but it's a guessing game to get the vanishing lines and depth compression correct - here's an easy way to control all that.
1: Create a layer and draw a shape of the surface you want the logo to be applied to, in this case, the side of the truck. I happen to know the dimensions of this truck (about 1:3), but if you don't know the exact dimensions, you can probably guess pretty close. I've also added a reference to the door on the side so my logo won't overlap the door on the truck. You can set a transparency to this layer if you like to make it a bit easier to position.
2: Create a new layer and apply your logo or whatever, positioning it on the "wall" layer you created before. This should look the way you want the graphic to look when looking at the truck from the side.
3: Select both of the new layers you created and pull up the transform tool (Comand-T Mac or Control-T PC). Right click inside the selected area and choose "Distort".
4: With both layers still selected, drag the corners of the selected area to the matching corners of the truck wall.
5: Hide or delete the "false wall" layer, and you should have a logo that is correctly placed with the correct perspective.