Over the years I have practiced the principle to not crop a photo after capture, but instead strive as much as possible to capture a composition that would also be one in the final photo. Most of the photos on this site are not cropped, and this usually works for me. However, some times I capture a photo only to discover later a new composition in the original capture that I think is better than the one I initially envisioned. An example follows below.
The whole photo as I originally envisioned and captured it with my Leica M 240 with Summilux 35mm FLE lens:
The cropped photo the way I decided to finalise it after spending quite some time figuring out why I didn't like the original composition:
These are now two radically different photos. The first one is to me a nice landscape photo. The second photo is an abstract / architecture photo. I like them both, but eventually the second photo is the one I decided to print and put on the wall. Let me know what you think! Enother Example follows below: