I'll often run through all of the overlays in the LR crop tool, just to have a look at how the image fits with the "traditional" rules of composition. I just wish there was a way of rotating some of them, for example the one that has a single line from top left to bottom right corners, with the lines at 90 degrees that run to the other two corners (I have no idea what it should be called) and the Golden Spiral. With those asymmetric guides a fixed orientation is a bit limiting. Oh and if you use the grid, remeber that it is based on the center of the image, not the top left corner.
Alan