The Rebbe's guidance on the wedding: when to hold it, customs, and expenses.
Choosing the date. Don't postpone a wedding without real need (IK 4273, 5965). Choose an auspicious time: the Rebbe recommended months associated with joy and redemption, such as Kislev, Adar, Nissan and Elul, or at least the first half of the month, when the moon is growing (IK 1583, 1956, 2122, 8163, 8509, 9353). Avoid Sefirah; after Shavuos is preferable to Lag BaOmer (IK 2571, 2657). Some days of Menachem Av are acceptable when other months aren't possible (IK 9352). Where necessary, there is flexibility, with proper guidance (IK 7161). Even after a loss in the family, the tradition is to hold the wedding as scheduled or even earlier (IK 7496, 8255). Postponing for an important reason is acceptable if all agree (IK 1908).
Chabad customs. Keep to the established Chabad wedding customs (IK 471, 5652): the chosson wears a kittel under the chuppah (IK 7204); the chuppah is held outdoors, and the shushvinin are chosen by agreement of both families (IK 7410, 7732); the maamar Lecha Dodi is said in full at the wedding (IK 6246, 6007); joyful Chabad niggunim (IK 562). On the tenaim text, see IK 4406. Holding the chuppah and sheva brachos in one central place helps everyone take part (IK 4245). The celebration must keep halachic standards of tznius, including regarding women's singing (IK 8734). The Rebbe objected strongly to pressure on a chosson to shave his beard for the wedding (IK 9001).
Expenses: moderation, not extravagance. Chassidic tradition favors moderation; the true richness of a wedding is its spiritual joy and the tzedakah given, not lavish spending (IK 3092, 7392, 7988, 10004). Burdensome customs that cause hardship and delay should be dropped (IK 4423). Both families should share in the expenses (IK 2721), and trust in Hashem to provide (IK 2466).
Hachnasas kallah: helping a chosson and kallah marry is a great mitzvah that brings blessing to giver and receiver alike, and even justifies interrupting Torah study (IK 1072, 6934, 7944).
See also: Marriage – Preparing for marriage; שידוכים – זמן בין אירוסין לחתונה.