One more thing to always think about in my opinion is that often time you forget what the subject of the picture is. Look at all of your vacation shots with waterfalls and mountains behind the people and do you notice that the background is in perfect balance, but the people are just little ants in the forground. Take pictures closer than you think in order to make them stand out more.
For example, my iPhone can't take a good close up shot, so all of my beer pictures with that camera come out looking like this.
It makes for a good shot that I can then throw online quickly, but not good if I am going to frame it.
When I want to frame it I get as close as possible while still being able to identify the subject in order to create a picture that makes you want to dive in.
If you keep this in mind you will be able to have enjoyable vacation shots and also have some fun with your camera. AND never center your subject. Always just a touch off center.