Exalted Guests - the Ushpizin
When the people of Israel leave their homes and enter the Sukka for the sake of G-d's Name, they achieve the merit there of welcoming the Divine Presence and all the seven faithful shepherds descend from the Garden of Eden, and come to the Sukka as their guests.
Waving the Four Kinds
One waves the Four Kinds [palm, citron, willow and myrtle] to and fro to Him who owns the four directions; up and down to Him who owns heaven and earth. That is to say: the four kinds are an allusion to G-d's having created all of existence, and that there is naught besides Him.
(Tractate Suka 37)
Rabbi Yehoshua ben Chanania stated: "When we used to rejoice at the place of the Water-Drawing, our eyes saw no sleep. How was this? The first hour was occupied with the daily morning sacrifice; from there we proceeded to prayers; from the prayers to the additional sacrifice; then to the House of Study; then eating and drinking the festive meal; then the afternoon prayer; then the daily evening sacrifice; and after that the rejoicing at the place of the Water-Drawing all night!"
(Tractate Sukka 53)
Keep It In Mind
You shall celebrate the holiday of Sukkot for seven days, in your gathering of the [fruits of] your deeds from the field.
After you have gathered in the bounty of the land, and your homes are filled with all manners of goodness -- corn, new wine and pure oil -- you shall dwell in sukkot, in order to remember that for forty years I sustained you in the desert. With this in mind you shall give thanks for your inheritance and for your houses full of plenty; do not say in your heart, 'My power and the might of my hands have wrought this strength.'
Rejoice With Constraint
And you shall rejoice in your festival and be happy - "ach sameach" (from the holiday Torah reading)
Without certain boundaries, unrestrained rejoicing can lead to levity and frivolousness. By using the word "ach" (literally, "but"), the Torah cautions that even while we rejoice, we must always be conscious of the reason for our rejoicing.
Shake the Lulav and Etrog
One of the main mitzvot of Sukkot is to take a palm branch (lulav), myrtle (hadas) and willow (arava) -- which have been bound together - join them with a citron (etrog) and shake them after reciting a special blessing.
The gathering of these four species is symbolic of the underlying unity of the diverse Jewish people. This mitzva is done on all the days of the festival of Sukkot except for Shabbat. Call a Judaica shop to purchase a set or go to your local Chabad-Lubavitch Center and "shake it" there.