To quickly straighten an image.
Lets say you have an image that needs the horizon leveled,or a crooked building straightened.
You could go into Rotate/Arbitary and adjust two or three times.
A much easier and faster way is ….
Go to the the eyedropper tool,click and hold down and select the measure tool.
Click and drag across the horizon or along the side a building, you now have a line on the image.
Now go to Rotate/Arbritary and you see photoshop as given you the exact amount and the rotation,so just click OK.
And it is automatically straightened, but it still as to be cropped.
If you wish to crop & straighten all in one move then choose the measure tool, drag across the image to get the amount that as to be rotated ,(it will be in the tool bar at the top of your screen) remember it or write it down.
Now go to the crop tool and select your crop by dragging,now you can rotate the bounding box to the calc. you have remembered or wrote down,you will see the rotate amount in the info window at the right of your screen.
When you have it click OK.
Now your image as been cropped & straightened in one move.
PS. When you’ve worked in Photoshop for 20 + years the little things are just taken for granted, we tend to forget not everyone knows it that well.
These tips are mainly for new users, mostly what I put here are simple little things that help greatly, but when starting out are very helpfull.