Erev Shabbos

The Rebbe urged his followers to recite the weekly sedra “sh’nayim mikra ve-echad targum” on Erev Shabbos specifically.
(Si’ach Sarfey Kodesh I, 11; II, 535. The custom of reviewing the weekly sedra before Shabbos is mentioned in Shulchan Arukh, Orach Chaim 285)

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The Rebbe and Reb Noson mention that one should also be diligent to cut one’s fingernails and dispose of them in an appropriate manner (optimally by burning them, or if that is too difficult, by burying them, or flushing them down the sink or toilet). Kabbalistically, these practices are related to the tikkun of the klippas nogah (the “glowing husk” in which good and evil are commingled).
(Likkutei Moharan I, 19:5; Likkutei Tefillos 19; cf. Shulchan Arukh, Orach Chaim 260:1; Rabbi Chaim Vital, Sha’ar ha-Kavannos, ‘Inyan Rechitzas Panav, 64d. The Gemara defines a “chassid” as one who burns his fingernails; Niddah 17a).

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After chatzos ha-yom, one should wash one’s entire body in hot water and immerse in a mikveh in honor of the Shabbos. After immersing in the mikveh, one should don Shabbos clothes. Reb Noson mentions these preparations in Likkutei Tefillos.
(Shulchan Arukh, Orach Chaim 260:1; Rabbi Chaim Vital, Sha’ar ha-Kavannos, ‘Inyan Rechitzah).