Taking care of many of our physical needs before Shabbat begins allows us to enhance our physical rest and emphasize our spiritual nature on Shabbat.
To prepare, we make or buy the food we will need for Shabbat, clean the house, and put it in order.  The custom is to shower or bath especially for Shabbat.
Before sunset on Friday, we turn on whatever lights we will need during Shabbat so that our homes are well lit. We leave the lights on until Shabbat is over (or we set timers to regulate when the lights go on and off since we cannot be involved with controlling them).
 

The International Dateline (IDL), which is 180 degrees away from Greenwich, England, crosses the Pacific ocean from north to south and divides a region of safek/doubt as to which day is Shabbat. This region's eastern boundary is a line 180 degrees east of Jerusalem, which lies between Hawaii and the US mainland; the western boundary is east of Shanghai. All countries in this region of IDL safek/doubt are island countries.
 
In a region of doubt, such as Tasmania, keep normal Shabbat (Shabbat d'rabanan) on local Saturday and keep Shabbat d'oraita on:

• West of mainland USA, but
• East of the IDL, and
• Not attached to the mainland.

• West of the IDL, but
• East of Shanghai, and
• Not attached to the mainland.

Note In all cases, you must still observe regular Shabbat on Friday night/Saturday.
Situation
You are in a place near the International Dateline (IDL) in which you are not sure which day of the week it is halachically: Shabbat or, if you are east or west of the IDL, Friday or Sunday.
What To Do
On the Friday or Sunday in question, there is no shvut (d'rabanan prohibitions, including muktza), so you may do all melacha d'rabanan WITHOUT a shinui. You may:

• Ask or tell a non-Jew to do anything, including a melacha d'rabanan or d'oraita.
• Ride in a cab or car driven by a non-Jew.

• Use electricity--except for heat or light—including turning on a fan or air conditioner (heat and light are forbidden by the Torah).
• Use the telephone. (Using a cellphone may be permissible--ask a rabbi).

• Carry from a private domain (reshut ha'yachid) to another private domain, even through a public domain (reshut ha'rabim); but you may not stop walking in the public domain and you may not put the object down in the public domain unless you use a shinui.
• There is no practical way to light candles, even using a shinui, but a non-Jew may light them for you and and you may say the blessing on the candles.
• Swim, surf, scuba dive, climb, and play all games that do not use melacha. You may not wring out clothes and if you are swimming or scuba diving, your swimsuit or wetsuit must be clean.
• Walk any distance (there is no techum Shabbat d'oraita).
• Kinyan. You may acquire items.

• Fly, including check in and getting on plane if:
  • The pilot is non-Jewish, and
  • You don't do any melacha d'oraita (including any writing) without a shinui.
• Use a computer if it automatically goes to sleep after less than 24 hours of not being used.
• Shower. However:
  • You may not use an “instant on” hot water system in which the water is heated as you use it; you may only use the hot water if it has a holding tank.
  • You may use only liquid soap; hard soap is forbidden.
• Ingest medicine (but you may not smear it on skin).
• Use some make up, such as rouge, mascara, eye shadow. You may not use lipstick.
• Open a refrigerator with light (and all other psik reisha d'la neicha lei).

• You may buy necessities on Friday or Sunday as long as:
  • The store owner is not Jewish (or if he/she is Jewish, does not write or print a receipt),
  • You do not write, and
  • There is no reshut ha'rabim.

You may also do melacha d'oraita if:

• You use a shinui (non-normal way of doing that action--this is forbidden d'rabanan on Shabbat but is allowed on the Friday or Sunday in question), OR
• Two or more people do the melacha together.

 
D'oraita, you may not:

• Cook food.

• Turn on lights (but you may turn them off).
• Carry from domains.
• Boneh – building any permanent structure.
• Write two or more letters of the alphabet.
• Drive--there is no practical way to drive using a shinui.
• Shave--there is no practical way to shave using a shinui.
• Use toothpaste (but you may use tooth-cleaning powder).
• Use skin cream--you may dab it on without smearing it.

However, you may do these following actions with a shinui on the Friday or Sunday in question, as follows:

• Cook food. You must put food in the cooking utensil first, then turn on the heat with shinui. You may turn off the heat even without a shinui.
• Turn on lights (such as with your elbow).
• Stop along the way when carrying from a private domain (reshut ha'yachid) to another private domain, even through a public domain (reshut ha'rabim). As a shinui, you may carry the object in your mouth (as long as it is not food), etc.

Note Carrying something in your pocket is NOT a shinui.

• Tear paper (such as putting toilet paper across knees and moving the knees apart).
• Write (such as with the opposite hand).

Flying East From Australia on Sunday If You Cross IDL from Friday into Saturday

A non-shomer Shabbat Jew may be counted as part of a minyan.
 

Do not check tzitzit on Shabbat or Jewish festivals.
Reason If there is something wrong, you might untangle them and thereby untie a knot, which is prohibited from the Torah.

Shiv'a that is interrupted by Shabbat resumes Sunday morning.

Pets may be given medicine on Shabbat and Jewish festivals.

For priority order of family members to light Shabbat candles, see Shabbat: Candles: Who Lights.
 

For how many Shabbat candles wives should light, see Shabbat Candles: How Many To Light.
 

You may not heat liquids by any method on Shabbat.  You may put a hot water urn on a timer from before Shabbat, but you may not add any water to the urn once Shabbat has begun.
 

You may not carry children on Shabbat in a public domain without an eruv. 
Situation An eruv breaks or is down on Shabbat.
What To Do Do not tell someone who is carrying a child, pushing a stroller, or in a similar situation that the eruv is down.
NOTE If a person is not carrying a child, pushing a stroller, etc., tell him or her that the eruv is down.

There are two requirements for Shabbat daytime kiddush: Say or Hear Kiddush Segments/Blessings and Establish a Halachic Meal (kovei'a se'uda):
 
1. Say or Hear Kiddush Segments/Blessings
    You must say, or hear, the Shabbat daytime kiddush segments/blessings and someone
     must drink at least 2 fl. oz. (59 ml) of the kiddush beverage:

• Say or Hear Kiddush Segments/Blessings
  • Torah segment(s): V'shamru bnei Yisrael (even beginning from al kein).
  • Blessing over at least 3.3 fl. oz. (99ml) of drink:
    • Borei pri ha'gafen (if on wine or grape juice), OR
    • She'hakol nihiyeh bi'dvaro (if on other beverage/chamar medina).

• Drink at Least 2 fl. oz. (59 ml) of the Kiddush Drink

 
2. Establish Halachic Meal (Kovei'a Se'uda)
    You must establish a halachic meal (kovei'a se'uda) shortly after saying or hearing
    Shabbat morning kiddush by either:

• Drinking Wine--at least 4 fl. oz (119 ml) of wine (or grape juice) within 30 seconds, OR
• Eating Bread/Mezonot--at least 1.3 fl. oz. (39 ml, or 1/6 cup) of bread or mezonot within four minutes.

Note The second half of making kiddush, “establishing a meal” (kovei'a se'uda), can be fulfilled simultaneously when you fulfill the subsequent, separate Shabbat requirement for “eating a meal” but in that case, you must eat 1.9 fl. oz. of bread.
Note If you make, or hear, Shabbat morning kiddush on any beverage except wine or grape juice, you must also eat at least 1.3 fl. oz. (39 ml, or 1/6 cup) of bread or mezonot within four minutes to establish the kiddush meal. If you do not want to eat bread or mezonot, only drinking at least 4 fl. oz. (119 ml) of wine (or grape juice) within 30 seconds will fulfill all the kiddush requirements. 
Note If you have not fulfilled the kiddush requirements, you may not eat other foods, such as fruit or fish at a kiddush.
Note   Once you have heard kiddush and either eaten the required bread or mezonot or drunk the required 4 fl. oz. of wine or grape juice, you do not need to say or listen to kiddush again if you eat your actual meal later (except if you need to say kiddush for other people who have not yet heard or said kiddush).

You may eat non-mezonot and non-bread food before praying Shabbat shacharit and without making kiddush, in order to avoid hunger or hypoglycemia (low blood sugar).

To fulfill the two requirements for Shabbat evening kiddush:

1. Say, or hear, the Shabbat evening kiddush blessings/segments:
   • Borei pri ha'gafen (on wine or grape juice only), OR
     Ha'motzi (on two challot if you have no wine or grape juice, as chamar medina is not permitted for Shabbat evening kiddush. See Challot for Evening Kiddush) AND
   • Mekadeish HaShabbat.
2. Establish a halachic “meal” (kovei'a se'uda) by either:
   • Drinking 4 fl. oz. (119 ml) of wine (or grape juice) within 30 seconds, OR
   • Eating at least 1.9 fl. oz. (56 ml) of bread or mezonot of any type (within 4 minutes) shortly after saying or hearing kiddush.

As on Jewish festivals, the minimum total volume of Shabbat kiddush beverage that must be drunk--usually by the kiddush-maker (mevareich) but it may even be by several people combined--is a cheekful (m'lo lugmov), as follows:

• 2 fl. oz. (59 ml) within 30 seconds of beginning to drink for d'oraita cases such as Shabbat evening kiddush (as well as first-night Jewish festival kiddush and all havdalas), and
• 1.7 fl. oz. (50 ml) within 30 seconds of beginning to drink for d'rabanan cases such as Shabbat lunch kiddush (as well as first-day Jewish festival lunch kiddush and all second-day Jewish festival kiddushes).

As on Jewish festivals, the minimum volume of kiddush beverage on which you may say Shabbat kiddush (or havdala) is a revi'it, as follows:

• 4 fl. oz. (119 ml) for d'oraita cases such as Shabbat (or first-day Jewish festival) evening kiddush, and
• 3.3 fl. oz. (99 ml) for d'rabanan cases such as kiddush for Shabbat lunch.