Light Shabbat candles wherever you will eat dinner.

To do Shabbat kiddush,

• Say, or hear, the Shabbat kiddush blessings/segments, and
• “Establish a meal” (kovei'a se'uda).

For details, see How To Do Shabbat Evening Kiddush  or How To Do Shabbat Daytime Kiddush.
NoteThere is never any requirement on an indvidual to drink kiddush wine (except at the Passover seder), but the kiddush wine must be drunk by one or more persons.

If you own any chametz, you must burn some of it in order to fulfill the commandment of burning chametz: this is a mitzva from the Torah! 

Say birkat ha'mazon instead of al ha'michya if you ate enough bread-like foods (mezonot) or bread-like food combinations (such as crackers with tuna salad) to be the volume of your normal biggest meal of the day. This is true even if:

• You had not planned to have a meal (for example, you planned to eat only one slice of pizza but then ate two more), and
• Did not wash your hands before the meal.

 

Don't fold clothes (including a talit) on an existing crease on Shabbat.

Note Taking three steps backward immediately before taking three steps forward, as instructed in some siddurs, defeats the purpose of taking the three steps forward. The purpose of stepping forward is to symbolically approach Hashem. If you step backward and then take your three steps forward, you are back to where you began and have not approached Hashem at all! 
If you do not have enough room in front of yourself to take three steps forward when beginning your amida, step back somewhat (at least a few seconds) before you say ga'al Yisrael. There is no need to take three steps back; a single large step that will give you room to take three steps forward is all that is needed.
By making a practice of taking three steps back, people have made the stepping backward part of the entire procedure, and it should not be.

Similarly, once you have finished saying the amida and walked three steps backward, wait at least three seconds before walking forward so as not to defeat the purpose of having stepped backward. Take as many steps as you need to get back to your seat--one step should suffice. 

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.

On Jewish festivals, you may not separate challa from loaves baked before the festival, as follows:

• In Eretz Yisrael, you may not eat bread from which challa was not separated if required (for more details, see Separating the Challa Portion and Challa Separation) until after the Jewish festival ends and you have separated the challa.
• Outside Eretz Yisrael, you may:
  • Leave one loaf until after the Jewish festival,
  • Eat as much as you want of the remaining loaves, and then
  • Separate the challa from the loaf after havdala.

You may dispose of a lulav in any way that is not degrading. So, you may drop it into a field or put it on a lawn--unless animals might eat it or step on it or if it will be subject to poor treatment before it decays.  Don't dispose of a lulav or etrog directly into the garbage. Burn, bury, or wrap them in a bag or one layer of plastic and you may throw it into normal garbage.

Say ha'tov v'ha'meitiv instead of she'hecheyanu when two or more people benefit from or enjoy something. 

B'di'avad, you may scoop out mayonnaise or mustard and spread it on meat and then scoop out more and then later use same condiment on dairy foods (and the same for dairy and later on meat) as long as any residual food is less than 1/60th of the total volume of food. But the preferred practice is to have two separate containers, one for dairy and one for meat foods.
 

If you recite birkat ha'mazon after se'uda shlishit over a cup of wine, you may only drink the wine if the meal ended before sunset.  

Jewish Festivals: Medicines: When To Take
Medicine generally may not be used on the d'oraita Jewish festival days.

Jewish Festivals: Medicine for Chronic Diseases
You may take medicine on Jewish festivals (whether d'oraita or d'rabanan) for:

• Chronic diseases, such as Parkinson's disease, or
• Any disease that affects your entire body.

Jewish Festivals: Medicine for Non-Chronic Diseases
You may take medicine on Jewish festivals for non-chronic illnesses, if skipping one day will prevent cure.  You may not take medicine for non-chronic illnesses if skipping a day will just delay your being cured (unless the disease affects your entire body--in which case, you may take the medicine).

Jewish Festivals: Medicines: When To Take: D'Oraita Festival Days
Here are the d'oraita Jewish festivals:

• First day of Sukkot, Passover, and Shavuot
• Seventh day of Passover
• Shmini Atzeret (8^th day of Sukkot)
• Yom Kippur
• Both days of Rosh Hashana (even though the second day is d'rabanan).

On these days, as well as on d'rabanan Jewish festivals, you:

• MUST take medicine whenever there is any question of a life-threatening disease or condition.
• MAY take medicine for a condition that affects the entire body (illness, weakness, etc.). Consult a rabbi if possible.
  ExceptionYou may not smear substances on skin UNLESS the illness is life-threatening, in which case even smearing is permitted.
• MAY use some medicines if only part of your body is affected by a non-life-threatening disease--consult a rabbi.

Jewish Festivals: Medicines: When To Take: D'Rabanan Festival Days
You make take medicines for any reason on d'rabanan Jewish festivals--even medicines not allowed on the first day of Jewish festivals--except:

• Medicines that you smear on skin.
• If the Jewish festival falls on Shabbat (which can only be second day of Shavuot).

L'chatchila, you should not bake uncovered dairy and meat foods in the same oven at the same time, even if both pans:

• Are non-liquid, AND
• Do not touch each other.

B'di'avad, both uncovered pans remain kosher—even if they touch each other, if both pans:

• Are non-liquid,
• Are clean and dry (on the outside), AND
• Do not contain spicy/charif food.

Here are requirements for a hot spring as a mikva:

1. The temperature may not be above 98° F.
2. If the spring and immersing area are separate, any pipes used to bring water into the immersing area from the spring must be at least 3" in diameter. Consult a rabbi.
3. The mikva area must contain at least 40 seah of the spring water.
4. The mikva area must be hewn of rock or poured concrete, etc., but may not be prefabricated in one piece, like a hot tub.
5. The water may not reach the mikva area via a pump.