I am guilty of only focussing on what I want. I will see a picture and take it. Only when I look at it, I realize that there's something completely distracting in the photo. ARGH! Now I have learned to look at what I want in, and then scan for what I don't want. Sometimes this means moving around. Other times it may mean removing items. Sometimes you have no choice and just hope that you can remove them later in processing.
In this shot I was trying to get the leaves and the dang dog just would not get out of the way. I love his expression which is clearly saying "whaddya mean I'm in the way? I add visual interest". I kept it for it's humour :)
Here are some shots where I managed to keep the correct focus (or sort it out with post processing):