One way to create a strong center of interest is to use vacuum focus. With vacuum focus you subordinate all other areas through desaturation and hue, leaving the most intense and alien color in the focal area. Marketers use this technique a lot, especially in movie posters.
Here are two recent blockbusters. In the Batman movie poster, you can see how overall the image is cool and desaturated. The burning bat symbol is in an intense complementary color to the overall blue hue, bringing your eye immediately to it. In the Sherlock Holmes movies poster it's a little more subtle, but the same technique is used. The overall image is a fairly desaturated blue-green, but the faces of the heroes — while also desaturated — are much warmer than the surrounding elements. Notice that even though some of those elements are also people, they are still of the desaturated green color.
They also portray very different ideas...in the Batman poster, the idea of the Batman symbol burning puts to question not only Batman's world going awry, but Batman himself. While the Sherlock Holmes is clearly about the celebrity actors and their characters and relationship. But that's getting a little sidetracked.
You can even use vacuum focusing on in traditional painting. Here are a couple landscapes using that technique.
The first image is by Dennis Sheehan. You can see how the overall feel of the piece is a cool green, but where the sunlight is striking through it is a much more intense and warmer color, kept to a fairly defined area. The second is a Jove Wang painting. Jove is quickly becoming one of my favorite artists. Here you can easily see the overall cool and desaturated colors and how the intense red and orange on the boat leap out at you, creating a strong center of interest.
When planning a painting, vacuum focus can be a great technique to bring about a strong center of interest and a stronger piece of work.