going to be cruel to be kind here
that photo is awful!!
you need to ask yourself what is the point of the photograph, what is its purpose, what is the focus of the image? That photo is a snap and nothing more it has no point of focus. You have a great subject there (the canal locks), these are great source of leading lines (another photographic compositional technique) - lines that lead the eye into the image and to the focal point of the photo. You need to assess the situation you are in and look around for the best way to photograph your subject.
the tree - thats a no no unless you wanted a photo of the tree, the flat path in the foreground - what a waste of space adds nothing and goes right across the image
Also as anthony mentioned the highlights (the whitest part of the image) is blown out, with digital photography you always need to meter for the highlights, control them and the shadow areas can have the detail brought out in photoshop later, its almost impossible to drag out details from highlight areas. To control the highlights you need to read the manual of the camera and learn how its metering works
got to go to work now, otherwise I'd post more. I'm not being nasty trim, its only by constructive criticism that you can learn to improve your photography. I'm off tommorow, so if you post some more I'll try and help you a bit more
but do a google on photogrphic composition, theres literally thousands of websites out there you can read that will help you learn what makes the difference between a snap and a good photograph