Binding the Lulav:
When: The custom is to bind the Lulav on Erev Sukkos inside the Sukkah. [The Rebbe would do so after midday.]
Who: Those who are meticulous bind the Lulav themselves. Women and children are not to do so for a man’s Lulav.
How: The Chabad custom is not to use the Lulav pockets. One makes two knots on the Lulav itself using Lulav leaves. One then places a Hadas on the right, left and center of the Lulav, placing the Aravos in between in an inconspicuous fashion. The Hadassim should cover over the 2 knots on the Lulav. One then binds three knots onto the Hadassim and Aravos, all three should be within the space 1 handbreadth (8 centimeters). It is proper to bind the Hadassim and Aravos towards the bottom of the Lulav in order to also hold on to them when doing the mitzvah. If one did not do so, he has nevertheless fulfilled the mitzvah.
Having the spine of the Lulav extend above the Hadasim and Aravos: The spine of the Lulav must reach at least one Tefach above the Hadassim/Aravos of the Lulav. The top of the spine is defined as the area it begins to split into other leaves. One must be very careful in this matter.