Indeed its quite easy. All you need is creativity and a understanding of lightning and shade effects. This tree is particularly easy because it just have a main trunk core, and the branches sprout out of it in a regular way. Want to see something complicated? See the spoiler bellow (and don't forget to fully expand it).
Now this tree I made before the pine tree, and believe me when I say this, it's the most complicated thing I ever worked with. First you have to create the medium sized branches with the smaller ones; then you combine with large branches pieces to create the larger branches; then you can mix with several large branches parts and with the trunk to create this large tree. I plan to publish this one day, but boy, I don't even know how I'll sort the several part this freaking thing has.