This is a great job for a first tutorial! There's a decent amount of text and great use of images to show how things are done, and it's a very quick, informative and enjoyable read.

I especially like the part where you describe how to shade using the dithering technique. A lot of people seem to lack the knowledge of how to do this properly, and you described it very simply and with great use of pictures. Everyone who reads this tutorial should know how to dither afterwards.

The only real critique I have is that I think you could have chosen a better color for the emoticon. Brown is hard to pull of well, but you did it rather nicely. However, the darkest color in the shading, the one right out by the edge, stands out too much, and the dithered pixels are very obvious.

Also, in my opinion, you should try to add dithering to the shading on the eyes and tongue as well, but that's only what I would have done myself.

Overall, great job, and a wonderful tutorial!