Center Focus will focus on the center of the frame.
Multi Focus automatically selects between a number of AF frames and focuses on the most contrasty subject closest to the center of the frame. For example, if your main subject (i.e. the subject you want to be in focus) stands beside some other object (behind or in front of your main subject) of greater contrast, the camera will focus on the latter object and your main subject will be out of focus. So, if you use Multi Focus as your default focus mode, this may explain why many of your shots are out of focus.
Area Focus deserves some explanation. I believe it is a focus mode that few uses, but there are certain situations where Area Focus is perfectly suited for and can help you capture a sharply focused shot where the other focus modes fail.(taken from http://www.photoxels.com/tutorials/tutorial-area-focus/)5) Shutter Speed
In photography, shutter speed is a common term used to discuss exposure time, the effective length of time a shutter is open; the total exposure is proportional to this exposure time, or duration of light reaching the film or image sensor. Shutter speed is one of several methods used to control the amount of light recorded by the camera's digital sensor or film. It is also used to manipulate the visual effects of the final image beyond its luminosity. (taken from http://en.wikipedia.org/wiki/Shutter_speed)6) ISO speed
The way to correctly meter a sunset is to meter on a small part of the sky away from the sun, any part of the sky that you want properly exposed, and then use those exposure settings while taking a picture of the sky with the sun (or other very bright parts of the sky) in it.
This technique requires that the camera either has some kind of exposure-lock (meaning you can lock the exposure settings while you move the camera to a different part of the sky), or that it has manual exposure.
The picture below illustrates this technique. It is important to remember this if you consider yourself a beginner, because you need to use this technique for many weather subjects! I will call this technique manual metering for the sake of reference. Not only does it apply to taking pictures that need to be properly exposed when a bright object is in the picture, but also to pictures with a large dark area in the picture that you want to keep dark on the photo (e.g. a photo of surface fog taken during the night). (taken from http://www.weatherscapes.com/techniques.php?cat=general&page=metering)8) White Balance
The Rule of Thirds is based on the fact that the human eye is naturally drawn to a point about two-thirds up a page. Crop your photo so that the main subjects are located around one of the intersection points rather than in the center of the image:
Golden Section rule
It has been found that certain points in a picture's composition automatically attract the viewer's attention. Similarly, many natural or man-made objects and scenes with certain proportions (whether by chance or by design) automatically please us. Leonardo da Vinci investigated the principle that underlies our notions of beauty and harmony and called it the Golden Section. Long before Leonardo, however, Babylonian, Egyptian, and ancient Greek masters also applied the Golden Section proportion in architecture and art.
To get a clearer sense of these special "Golden" composition points, imagine a picture divided into nine unequal parts with four lines. Each line is drawn so that the width of the resulting small part of the image relates to that of the big part exactly as the width of the whole image relates to the width of the big part. Points where the lines intersect are the "golden" points of the picture
One side of the picture is divided into two, and then each half is divided into three parts. The adjacent side is divided so that the lines connecting the resulting points form a diagonal frame. According to the Diagonal Rule, important elements of the picture should be placed along these diagonals
(taken from http://www.colorpilot.com/comp_rules.html)