Depth of field. Read up on that.
Think about composure and the way you like it. You will 'see' settings, places, things etc that just speak photo in your mind. Capturing it is done with the camera, but how you want it to 'look' if you will is your personal preference. However, there are guidlines [and dos and don'ts] in the realm of photography (like exposure, f-stop, shutter speed and all that stuff) but those are really more technical things; how things work.
If the photo looks good in your eyes, then by all means its a good photo. Thats what really matters, imo. Accept critique of your photography as contructive critcism (and/or how to improve upon your photo skills). Everyone has their own preferences.