Use the online Avatarize Yourself tool (see Resources) to create an animated, digital image of a three-dimensional Na'vi head with your facial features. The process is completely automated, and merely requires you to upload a photo of yourself from your hard drive or Facebook profile. For best results, use a quality photo in which you are looking directly at the camera and not smiling.
Make a Na'vi version of yourself completely from scratch, using an image manipulation program such as Photoshop or GIMP. Follow one of the detailed tutorials found on websites such as Blueprint Media Design and Web Design Library. The main skills needed to successfully create an avatar include hue/saturation editing, to change the skin color, and proficiency with deformation tools, to increase the size of the eyes and broaden the nose.
Try Khalypso's avatar creation tool if you don't care whether the Na'vi looks like you but simply want to design its costume and skin patterns. This Flash-based web program allows you to mix and match various accessories, hairstyles and coat markings to create a cartoon image of a Na'vi, which you can then copy to your clipboard and save.