a. Plastic covers which cover light switches to avoid someone inadvertently turning them on, and plastic covers which cover electrical outlets to prevent babies from touching them, are not Muktza, because as protective covers they constitute a K’li SheMelachto LeHetter (HaRav Shlomo Pearl, Shlita).
b. The Sefer Pele Yoetz writes that if one speaks about inappropriate subjects on Shabbos, this also falls within the guise of “Chillul Shabbos”, and decries those who use terms such as “Bilti Amiras Shabbos”, or “Nisht Of Shabbos GeRett”, and then proceed to talk about business, construction and other things or acts that you cannot do or perform on Shabbos itself. In a similar vein, Rabbi Dovid Ribiat, Shlita, in his Sefer The 39 Melachos writes that one cannot say, “I am returning this food to the refrigerator so that it will remain fresh for tomorrow”, or “Let’s soak the dishes now so that washing them after Shabbos will be less difficult.” Rabbi Ribiat adds that Shabbos is also not the time to tell sad stories or recount troublesome events to a friend, which may cause him (or you) anguish or emotional distress.
c. The Steipeler, Z’tl, (Karyana D’Igarta I, Letter 304) provides the following fundamental insight: If one would know for certain that if he violated a particular Issur D’Oraysa on Shabbos he would be punished with this kind of infection or that kind of severe headache, and if he knew that if he sullied that Issur DeRabannan, he would be punished with that kind of virus or that kind of writhing backache, he would be careful to stay away from this Kula or that Kula, and would distance himself from even the possibility of getting close to the Aveira. If, the Steipeler says, we are scared of one of these illnesses, a temporary illness in this passing world, all the more so should we be concerned of a punishment with much more long-lasting and devastating results. Shabbos is the “Os”--the sign of our special, eternal relationship with Hashem--and if we abuse it, or do not treat it with the respect that it deserves, we are sadly and regretfully abusing this relationship--a relationship which is intended to infuse us not with laxity and superficiality--but with holiness and depth--as the Torah testifies (Shemos 31:13) the purpose of Shabbos is “Lodaas Ki Ani Hashem Mikadishchem--to know that Hashem sanctifies us!”