A good way to isolate the subject is to use a wide aperture, (a low f-number), and by making sure that the focus is on the subject that you want to stand out.  By doing this, you will make both the background and the foreground blurred.

I reinforce this in my composition by using the rules of thirds.  It is also important to make sure that your horizon is straight.  You can do this when editing, by cropping and rotating the image slightly.

The red against the green helps to make the subject pop. What can you do to reinforce your subject today?