Predefined particle systems that come with Cocos2D are a good way to start, but in many cases, you will want to create a custom particle system and tweak all the properties. This way you will have to build and run the game after each change to test the particle system. This is not very efficient.
There are a few tools that can help you to design a particle system and Particle Designer 2 is definitely one of the best. Let's use it to add a sun to our game scene: