Determine the natural lean of the tree. This is the direction you will encourage it to fall. Attempting to fell a tree against its natural lean is very dangerous and should only be done by highly experienced lumberjacks.
Create a notch and hinge in the tree trunk. The notch is a cut that is about 90 degrees and about one-third of the distance into the tree trunk on the side of the tree where you want It to fall. Picture the notch as a slice of a piece of watermelon, with the saw cutting at a 45-degree angle from a point about 3 feet above the ground to a distance of one-third of the way into the tree and a matching 45-degree cut below that one and headed upward to join the downward cut. When the notch is pulled out, the part of the tree that is left is the hinge.
Cut a horizontal bore hole from the inside middle of the notch directly through the heart of the tree. It’s vitally important that the saw be held level so that the bore will be met when cutting from the other side of the tree. Do not cut much past the center of the tree. This cut from the inside of the tree takes away the strength of the support from the center of the tree and avoids the possibility of the tree splitting up the middle as it falls.
Turn to the back of the tree behind the notch and begin to cut through the hinge that's holding the tree up. Keep the saw level with the horizontal inner line of the notch and cut through the wood. As you reach close to the middle of the trunk, you should meet up with the bore hole cut from the inside of the tree. Continue to cut through the hinge to the notch. As you approach the notch, the chance of the tree falling greatly increases. Be prepared to shut off the saw and backpedal quickly away from the direction that the tree falls.