One should prepare the zero’ah [roasted shank bone] and roasted egg before Shabbos. One should be careful not to say that he is roasting the bone for Pesach. Bedieved if one said this, it is ok (Mishnah Berurah 469:2). If one forgot to roast them before Shabbos, the Mishnah Berurah (473:32) writes that one may roast them on Yom Tov night. When roasting the bone, one should have intention to eat it on Yom Tov day (not at night as it is forbidden to eat roasted meat/chicken on seder night). When it comes to the roasted egg, however, one should cook it with intention either to eat it during seder night, or the following day.
One should prepare charoses on erev Shabbos, if one didn’t add enough wine, one may add more on Yom Tov as there is no issur to do lisha [kneading] on Yom Tov. If one never prepared any charoses before Shabbos, the Pri Megodim (444, M.Z. 2) writes one can make it and he should grind the ingredients with a shinuy [in an abnormal manner], like every Yom Tov (see Rema beginning of 504).
One should prepare salt water before Shabbos, if one forgot, he may do it on Yom Tov night with a shinuy, and should add the water before the salt (Chayei Adam, Klal 130, Dinei Haseder Beketzorah, s.k. 1, and Kitzur Shulchan Aruch 118 end of sif 4 – however, see Pri Megodim 473, Eishel Avraham, s.k. 5 which omits any mention of shinuy, see also Mishnah Berurah, s.k. 21, which just says to make a small amount. See Tosfos Chaim on the Chayei Adam who brings those who ask on the Chayei Adam, why a shinuy is needed).
After washing the lettuce for marror, one should make sure to keep it in the fridge so it doesn’t get withered out (see Mishnah Berurah 473:37 who brings a machlokes haposkim in regard to using withered out maror, however, see Shaar HaTziyun s.k. 48, who says that those who are stringent clearly never saw the rishonim who rule leniently.) However, one shouldn’t keep the lettuce soaking in water, as then there will be a problem of kevushin.
If it is possible to grate the horseradish on erev Shabbos and store it in a container which will keep the sharpness, then that is best (as according to the Magen Avraham it is forbidden to grate on Yom Tov, even with a shinuy). If, however, one is worried that the sharpness will go away, then one should grate it on Yom Tov with a shinuy, i.e. he should grate it over a cloth and not onto a plate (Mishnah Berurah 504:19).
If one plans to mix white and red wine together, he should do it before Shabbos, to be concerned for those opinions who hold that there is tzove’ah (the melachah of dying) on food. However, if one didn’t, then on Yom Tov itself one should first pour the red wine into the cup, and then add white (see Shu”t Shevet HaLevi 10:56).
The minhag in many houses is to cover the taps with a sieve-like cloth for Pesach, one should do this before Shabbos.
If one has special Yom Tov clothes, some say it is forbidden to put them on, on Shabbos before going to shul for Maariv on Yom Tov night, as it is a problem of hachonah [preparing] and a zilzul [disgrace] to Shabbos. Therefore, one should either start wearing them on erev Shabbos, or wait until motzei Shabbos to wear them (Chok L’Yisroel 52).
However, some say that one may change into the special Yom Tov clothes after Mincha, as one can say he is changing his clothes as he doesn’t want to be wearing clothes that he ate chometz in when Pesach starts. However, when it comes to clothes which don’t touch any chometz, one can’t say this (Ben Ish Chai, Parshas Tzav, ois 4).
Practically, if one puts them on whilst there is still a decent amount of Shabbos left, then one benefits from them on Shabbos as well, and there is room to be lenient (see Kaf HaChaim 529:23).
If it is possible, one should set up the seder table before Shabbos, so that he can start the seder as soon as possible on motzei Shabbos.
