This tutorial can be helpful to everyone; from newbies to intermediate artists. You might not actually call it a tutorial and this is not by me. I was making a tree and posted it on Pixelation where other fellow members helped me and posted a great tutorial!
Here is the link to the tutorial: http://www.wayofthepixel.net/pixelation/ index.php?topic=14143.msg132173#msg132173
Thanks to Cyangmou for this excellent tutorial!
Feel free to reply and post more tutorials, if you know any.