Of the two shots below which do you think is the best?
For some reason most people will say the 2nd one despite it containing the same elements as the 1st but just positioned differently. Why is this? I don't know I'm not a psychologist, that's just the way it is. How you do it is easier to explain and all you need is any old camera.
When you look through your viewfinder/at the screen on camera imagine that it is divided into thirds both horizontally and vertically. Where 2 of those dividing lines meet is the best area to place your subject.
In this shot the photographer picked the upper-right position for the subject so that we could see the full shadow and most of the tracks that lead to the seagull.
Also always consider your sky and ground. Which looks more interesting? If the sky is best place the horizon on the lower divide. Is the sky dull and grey but the ground nice and textured? Put the horizon on the upper divide. You'll be amazed how much this improves those shots of landscapes.
Like any rule it's there to be broken but try taking a few shots with these things in mind and you'll be surprised how suddenly a nice shot becomes a great shot.
*pictures swiped from photoinf.com but I'll take some myself soon to illustrate this instead.
Nick