http://design.tutsplus.com/tutorials/how-to-create-a-detailed-key-illustration-in-adobe-illustrator--cms-23065

In the following steps you will learn how to create a detailed key illustration in Adobe Illustrator, with a romantic message perfect for Valentine’s Day.

For starters you will learn how to set up a simple grid and how to create the main shapes using basic tools and techniques. Next, you will learn how to add shading and highlights for these shapes using basic blending and vector shape building techniques, along with a bunch of effects and the Appearance panel. Finally, you will learn how to add a nice ribbon using a simple calligraphic brush, some linear gradients, and the Type on a Path Tool.