Cropping an image
Rule 1; Save your original image and crop a copy. If you get it wrong, or want a different aspect ratio later you can always go back to your original.
Do a "border patrol" let your eye wander around the edge of the image and see if there is half-a-something, or something brightly coloured distarcting you eye near the edge - simple cropping can save a lot of editing!
Next look at the image crtically; there are usually several images within an image - I have shown a few here. The choice is yours BUT check you have evaluated all the choices.
Don't forget cropping is an ideal time to straighten any horizontals or verticals. You will ALWAYS get a negative judges comment if the sea horizion is as much as one degree off!
Note the drop down; you can crop to the size you need which will make printing easier. I often crop to 16:12 which is the default size for the camera club. You can, of course, free-form crop (any width, any height) if your image has multiple distractions.
It occasionally, but rarely, works to crop tightly on an image. You usually have to leave some "breathing space" around the subjects. As with every rule, this one can be broken, just be careful.
Also leave some room for the subject to "travel" into the empty space. i.e. for a ship leave some sea for the ship to sail into.
If you're cropping a portrait, crop it purposefully. Take off the legs, or the body, not just a bit of arm – that will look like a mistake.
An example (from Julia) of a tightly cropped image that works fantastically well.