Thomas Scholes showed this to me a couple of years ago, but I've met lots of people who don't know it, and I think it's worth sharing for people who do backgrounds in Photoshop - particularly people who struggle with things like repeating windows, telephone poles or whatever.
We'll start with a very simple 1-point perspective set of railroad tracks. We need to put ties on these tracks, and we want them to get smaller and closer together as they go to the vanishing point. We *could* measure all that stuff...or...
Draw one tie, the closest one. Then copy it with 'control-j' and do a 'Free Transform' with 'control-t'. You'll see a circle in the center of the transform box. Move that circle to your vanishing point, even if that is outside of the box. Hold down 'alt' and 'shift' and grab and move a corner of the transform box. The tie will move and resize along your 1-pt perspective grid!
Ok, that's awesome, but it's just one tie....BUT...after you've finished placing the second tie, be sure you have that layer highlighted and hold 'control'+'alt'+shift+t. That repeats the transformation and copies it to a new layer! You have the 3rd tie, and it has been transformed in relation to your first one...so you have 3 ties in perfect perspective! If you keep repeating that command, you can get all of them placed in seconds!
Say you needed to place power lines the same way. Photoshop remembers the transform until you do a different one, so you can draw something else, and have it match the same perspective transforms as before by using 'control'+'alt'+'shift'+t.
I've picked the most ridiculously simple example of this, but it is GREAT for things like high-tech corridors, lights, arches on classical architecture, windows on high-rises or whatever. I often use transform-in-perspective as a reference when placing people in the background to make sure they are the same basic height and size as foreground figures.
Try it, I think you'll like it!
As always, please share if you found this helpful, and thanks for reading :)