When it comes to photography, there are particular things to watch out for and particular things to use towards your advantage. A key element in almost every photograph is the background. Rarely will you see a great photo that has not adequately used the background to complement the photo. A photographer may have one of the most beautiful or breathtaking subjects to photograph, but with using the background to their advantage, the subject will be wasted.
One method of using the background to complement the subject is when a photographer uses depth of field to blur the background. The blurred background will naturally draw the viewers eyes towards the subject which will be crisp and clear. The way that a photographer does this is by using a larger aperture. Further developing off of the blurred background, a colorful background which is blurred will further enhance the image. A plain color background will not be as effective because it will not appear as blurred and will decrease the color of the shot resulting in a duller photograph.
Choosing a complementary background does not mean that you should always blur the background. There are definitely times where you want that background in the shot. There are a couple of things to look out for in this case. First, you will want to make sure that there are no other subjects in the background that will detract from the photo. You want to make sure that any distractions are obscured. Second, you should always look to avoid subjects merging. It is always frustrating when you get home only to realize that that great shot of your friend looks like they have a tree branch growing from their head.
With a combination of the two above tools, it becomes easier to help create complementary backgrounds. These tools will not work every time, but with a little practice they will help improve the vast majority of your photos.