Hallel
Full Hallel is recited. When reciting Hallel, one may not interrupt it – other than for those things that one may respond to during the Brachot of Kriat Shema. [i.e. if the Chazzan recites Kedushah, one responds Kadosh, Baruch and Yimloch. When the Chazzan says HaE-l Hakadosh, one answers Amen. When the Chazzan says Modim, one answers the three words Modim Anachnu Lach. When the Chazzan recites Kaddish, one answers Amen Yehei etc, and Amen to D’Amiran B’Almah. One also answers Barchu and Amen when the Brachot are recited before and after an Aliyah or Haftorah.]
It is preferable to recite Hallel with the Minyan. If one is not up to the Minyan, this creates a dilemma; on the one hand it is appropriate to recite Hallel with the congregation, and on the other hand, it is appropriate that one davens in the correct order. For this reason, the Chabad Rebbeim were always punctilious about being up to Hallel when the Minyan recited it on Chag.
If one forgot to recite Hallel, he should recite it with a Brachah as soon as he remembers, as long as it is not yet sunset. If one mistakenly recited half-Hallel, he must repeat the entire Hallel (without a Brachah).
Hosha’anot
For Hosha’anot, a Torah is held at the Bimah (preferably by someone who does not have a set of Daled Minim or someone in the year of Aveilut who doesn’t circle the Bimah). The Aron Hakodesh remains open throughout Hosha’anot.
When reciting the Hosha’anot unique to that day, most communities recite the phrases aloud after the Chazzan. The Chabad custom is that the initial phrases are recited quietly at one’s place, each phrase being preceded with the word Hosha’anah. According to Chabad, the phrases from the letter ‘Samech’ or ‘Ayin’ onwards are recited aloud after the Chazzan, with each phrase preceded and followed with the word Hosha’anah. According to all, these phrases are timed to coincide with one complete circuit around the Bimah.
During Hosha’anot, the Lulav is held with the right hand and the Etrog with the left. The Rebbe would generally hold them joined together and touching his chest.
One without Daled Minim does not circle the Bimah. [It is best to borrow a set in order to participate.]
The last Pasuk (i.e. L’Maan Da’at) is said aloud when the Sefer Torah is returned to the Aron Hakodesh. One holds the Daled Minim until this time.
On Chag, one may return the Lulav to the moist towel or water that it was already in. One may also place it in another moist towel or other water, as long as they were prepared before Chag. One may add water to either of these, but may not completely change the water.
