Actually, it's a combination of things as lighting, shaders, etc. which all work together to form the illusion of 3D. Dragon mentioned a couple rendering/lighting options. For further info on what he's talking about, search around for info on "Global Illumination" and "HDRI" so you have a better understanding of what they are. While that's all well and good, IMHO you should pay attention to simple shader creation before getting mired down in that.

Creating a basic plastic isn't too difficult. Try assiging a blinn to an object and play with its eccentricity (0.1) and specular roll off (1.0) settings. Also change the specular color to pure white. Do an IPR render and drag-select the rendered object. You should see a green box around the portion you dragged. Now, you can fine-tune the blinn's settings and get auto-updates in the render window.