You may say ma'ariv on Friday afternoon (erev Shabbat) as early as plag ha'mincha (1 1/4 halachic hours before sunset), as long as you say mincha before saying ma'ariv. So, if it is now plag ha'mincha, you may say mincha and then follow it as soon as you wish with ma'ariv.

You may tell a non-Jew to do melacha for Oneg Shabbat. 

A Jew known not to observe the laws of Shabbat is not accepted as a witness under Jewish law. However, if it is known that the person would not lie, he or she may be trusted in some cases.

When Tenth of Tevet occurs on a Friday, you may not start Shabbat early in order to cut short the fast.  That is, you may not eat until dark, as is normally the case.
 

You may use water from a well on Jewish festivals (as on Shabbat) via an automatic pump that fills a reservoir once the water level drops. But you may not operate the pump directly and you may not turn the pump on or off.
 

Although the traditional time to say kiddush levana is after Shabbat, you may say kiddush levana from the third day (three periods of 24 hours) after the molad until 14 days and 18 hours after the molad.  Ideal is after seven 24-hour periods.

You must not travel during any part of Shabbat if you are flying for pleasure. You must therefore leave with enough time to land and get to an accommodation before local Shabbat starts at your destination.
 

You may twist or untwist twist ties on Jewish festivals (and Shabbat), but only if you intend them to be a non-permanent seal.

Girls and women may remove makeup or nail polish on Jewish festivals (or Shabbat).
 

You may practice blowing a shofar on Rosh Hashana (unless it coincides with Shabbat!).

You may add personal requests to the amida on weekdays (not Shabbat or Jewish festivals) in these prayers:

• For livelihood:
  • In the amida's 9^th paragraph (bareich aleinu), between mi'tuvecha and u'vareich shnateinu.
• For a general request:
  • In the amida's 16^th paragraph (shema koleinu), before ki ata shomei'a.
  • Even better, just before saying yihiyu l'ratzon.

 

You may squeegee a floor--as is commonly done in Israel--on Jewish festivals (or Shabbat)), but you may not push the water onto earth or plants.
You may mop up a local spill, but only without squeezing out the rag or mop.
 

You may not wash or hang up wet laundry on Jewish festivals (or Shabbat).  The halachot for drying laundry depend on whether you use a clothesline or a dryer:
Jewish Festivals: Laundry: Clothesline
You may only take down laundry on Jewish festivals if it was dry before sunset at the start of the festival, and only if you don't:

• Transfer the laundry from one halachic domain to another (hotza'a), or
• Give the impression that the laundry had been washed on the Jewish festival (mar'it ayin).

If laundry on a clothesline is still wet at sunset before the festival, the laundry is muktza and you may not take it down or use it during the festival. This is different from the case of a dryer.
Reason On the clothes line, there is no certainty that the laundry will dry during the festival (it might rain, it might be cold or cloudy...), so the person may not have in mind that it will dry during the festival.
Jewish Festivals: Laundry: Dryer
Laundry in a dryer (even if it was wet at sunset) that was turned on before sunset beginning the Jewish festival (or Shabbat) is not muktza, even if you do not intend to wear it.  You may remove the dry laundry from the dryer on the Jewish festival as long as no light goes on.

You must eat a second meal on Jewish festival (or Shabbat) day with 1.9 fl. oz., or 56 ml, of bread--even if you already said ha'motzi and ate bread at kiddush.

For women and public consolation (nichum aveilim), see Women and Public Consolation after Kabbalat Shabbat.