I would have liked to have gone even tighter, showing only a portion of the lizard, but there just wasn't enough photo to work with. I like PhotosGuy's advice to take several different shots so that you have more of a choice in your cropping. (This example shows the downside of cropping too far and losing resolution and detail.)
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Just for your reference, my goals were to fill the frame, leave some leading space, and put the focal point (the eyes) at the inside of the Golden Spiral (sounds complicated but it's very similar to the rule of thirds). Anyway, my point is that this crop looks pretty good and there were virtually no "artistic" decisions made. I simply took the tightest crop possible without cutting off any lizard, left a little open space to the upper right, and then aligned the eyes on the spiral overlay in Lightroom. With most photos, following these basic rules gives a good no-thinking-required starting point for the final adjustments.
Also, could you please make us legal by turning on "Image Editing OK" in your profile? Thanks
Edit: regarding your question about how far can you crop without messing up the image, the image I attached is 600 x 293 pixels. If you want to print at 240 dots per inch, this image should only be printed at about 1.25" x 2.5" (barely big enough to use on a business card). However, if I had started with the original Raw file, it's likely that there would have been enough pixels to print at a larger size. If you had zoomed in on the lizard, the Raw file would have had enough information to allow printing at a very large size.