I like this picture because it looks a little like a grumpy radish.
Draw marks at the base, top and furthest sides of the tree first. Then very draw in the very basic outline.
Don't worry about getting every individual branch, just the things that stand out for you from the picture.
Then add some detail:
Next (the important lesson about shading) - nothing on this tree is white, so shade everywhere there is tree.
Then you can worry about details and making it look good. I thought I knew what I was doing here, but I admit that these shadows are quite crap. But, it still looks a little like a radish!