1) Make a cylinder, give it a few stacks (if youre using Max, give it some tapering so it will get skinnier/twist towards the top)
2) Grab some edge loops, scale them different
3) Grab some individual verts, push and pull them around to add some difference to the trunk of the tree
4) Make some flat planes, rotate them around and make one edge touch the tree trunk.
Voila, just texture the the trunk with some bark and the planes with some leaves (use a 32bit TGA to include the alpha layer in the texture) and youre solid!