It is the custom to engage in a mitzva shortly after breaking the Yom Kippur fast by beginning the building of one’s sukkah on Motz’ei Yom Kippur, and to complete building it during the ensuing days.
Constructing a Sukkah:
The sukkah should not be constructed under a tree, even if the branches are very high above the sukkah. If there are minimal leafy branches above part of the sukkah, the sukkah is likely valid, but oftentimes one may not sit under that part.
A canvas sukkah should be tied down securely in a manner such that the walls do not sway in the wind. When purchasing a canvas sukkah, it is commendable to purchase one that has halakhically valid “lavud straps.”
If one has a “shlak” (removable rain roof), it should be open (see note for explanation) when placing the schach atop the sukkah.
There are several types and brands of schach mats available. One should use only a mat with a reliable hechsher.
One should not be ma’amid (directly support or hold down) the schach with anything that is not valid for schach (e.g., metal, plastic, or rope). (This stipulation generally applies also to substances that are used to hold a mat together.) However, this stipulation is a chumrah (stringency), not an absolute halacha. Therefore, if one is invited to eat in a sukkah in which the schach has such a ma’amid, one is not required to decline the invitation.
One may even l’chatchilah (initially) secure schach to the sukkah by laying a 2x4 or a 2x2 “beam” over the schach at each end and then tying the beams securely to the sukkah and/or to each other with rope or tape. I.e. the schach will be “sandwiched” between the beams. The tying should be done on an area of the beams at which there is no schach. For a large sukkah, it would be advisable to place several such “beams” across the schach to hold it in place.
Coming next: Laws of eating in the Sukkah.
32] Rema O.C. end of 624:5; Rema O.C. 625:1; see also M.B. 625:2.
 See S.A. O.C. 626:1.
 The reason is that there are Poskim who hold that if the walls blow 3 tefachim (3 handbreadths = 9-12 inches) from its resting position, the walls are not valid to serve as walls for the sukkah (M.B. 630:48 and Igros Moshe O.C. 5:40 #2; cf. Chazon Ish O.C. 77:6).
 These are straps that are affixed horizontally along the bottom 10 tefachim (approximately 40 inches) of the sukkah, and which are interspersed approximately 9 inches from one another. The “lavud straps,” which are pulled taut, serve as the halachic walls of the sukkah, thus obviating the need to tie the canvas securely.
 For a shlak that is lowered and raised (such as a skylight or roof), “open” means fully raised so that the shlak is not hovering above the schach. For a shlak that rolls out as a covering over the schach, “open” means rolled closed such that the shlak is not covering the schach.
 See S.A. O.C. 626:3.
 Kosher supervision. The reason is to ensure that the mat was made in a way that it cannot be mekabeil tum’ah (contract ritual impurity), which would render it invalid to be used as schach. See S.A. O.C. 629:2,6. In addition, even if the mat is not mekabeil tum’ah, the string that holds it together might be, which would create an issue of ma’amid; see the next paragraph in the text. If one cannot possibly purchase one with a reliable hechsher, one should consult with one’s Rav well in advance of Sukkos.
 See M.B. 628:17 and 629:22.
 See S.A. O.C. 629:7 with M.B. 629:22.
 Doing such is permitted since the schach is not being supported by the rope/tape; rather, the beam, which is holding down the schach, is being supported by the rope/tape. (This concept is colloquially called ma’amid d’ma’amid – a support of the support, which is allowed even according to the chumrah; see M.B. 629:26; cf. Chazon Ish O.C. 143:2.)
 Im Yirtzeh Hashem (G-d Willing).