Friday night, it is a nice custom for men to say va'yechulu with at least one other man. It is best (but not required) to say va'yechulu with the entire minyan.
Reason The idea is that we are attesting (with other people, as in a court) to God's having created the world.
 

Pot lids are treated as if they are utensils.

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).

When you have food mixed with non-desired substances, you may remove the non-desired ones by picking up the entire mixture and letting the non-desired elements fall away.

On Jewish festivals, when walking into the path of an electric eye:

• You may walk into one that prevents a door from closing.
• You may not walk into one that causes the door to open.

Say birkat ha'mazon at either place if:

• You eat in one place, intending to continue your meal in another place, AND
• You ate at least 1.3 fl. oz. (39 ml, or 1/6 cup) of bread at either place.

Trees planted at least 45 days before Rosh Hashana (that is, by Tu B'Av) are considered to be one year old on that Rosh Hashana.

If kosher supplements are not available or are not as good as the non-kosher ones, you may use non-kosher nutritional supplements, including non-kosher gelatin capsules:

• If you are sick (disease, headaches, weakness....), or
• To improve your health if you have deficient nutrition

You may place a siddur or chumash flat on chair seat or bench on which no one is sitting, but it is an act of piety to stand it up on its edge. 
To sit on a bench or other seat where a holy book rests, raise the book up at least a little; a single piece of paper is sufficient elevation.
NOTE If you are sitting on a bench and someone puts a holy book on the bench, you must stand up or raise the book off the bench. You may not stand a siddur, chumash, or other holy book up on its edge on a bench or pew in order to be allowed to sit on that bench.

Each dead person needs kaddish to be said for him or her:

• By at least one person.
  Note If more than one person who was close to the dead person (such as a relative) says kaddish, it is a merit for the soul of the dead person.
• At least once a day. 
  Note More frequently is commendable, since kaddish relieves a dead person's soul from gehenna.

A non-Jew is not permitted to observe Shabbat completely. He or she must do at least one violation. This is relevant for people who are in the process of converting to Judaism.
 

If a boy born in Adar 2 will be bar mitzva in a year with only one Adar, his bar mitzva is in Adar, not in Nisan. If a boy born in Adar 1 will be 13 years old in a year with two Adars, his bar mitzva will be in Adar 2.

We are required to eat two meals on Jewish festivals, each preceded by kiddush, one in the evening and one in the morning. For both meals for each Jewish festival day (and all three meals on Shabbat), say ha'motzi over two complete loaves of bread, each of which is at least 1.3 fl. oz. in volume. 

Source of Saying Jewish Festival Kiddush
Some kiddushes are commanded by the Torah (d'oraita); the others are from Chazal (d'rabanan), as follows:
Kiddush d'Oraita

• First night of Jewish festivals
• Night of seventh day of Passover
• Night of Shmini Atzeret.

Kiddush d'Rabanan

• First day of Jewish festival
• Second night of Jewish festival
• Second day of Jewish festival
• Seventh day of Passover
• Eighth night of Passover
• Eighth day of Passover
• Shmini Atzeret day
• Night and day of Simchat Torah.

Source of Jewish Festival Kiddush Location
Saying Jewish festival kiddush at the place where you will eat your meal is a rabbinical (d'rabanan) enactment.
Jewish Festival Kiddush-Meal Quantities: Evening

• For evening kiddush for a first-night (d'oraita) Jewish festival, a minimum of 4 fl. oz. (119 ml) of wine must be blessed on and at least half must be drunk.
• For evening kiddush for a second-night (d'rabanan) Jewish festival, a minimum of 3.3 fl. oz. (99 ml) of wine must be blessed on and at least 2.0 fl. oz. must be drunk.
• For the evening meal, as on the first two Shabbat meals and for all required Jewish festival meals, a minimum of 1.9 fl. oz. (56 ml) of bread must be eaten within four minutes.

Eating Requirements for Jewish Festival Morning Kiddush
There are two separate eating requirements during the daytime. They may be combined (say/hear kiddush and start the main meal right away) but are often done separately (say/hear kiddush and then eat some light foods and beverages; the main meal is eaten later in the day).
Note Since eating and drinking requirements on all morning kiddushes (both Shabbat and Jewish festivals) are d'rabanan, the required beverage amount for morning kiddush is only 3.3 fl. oz. (99 ml) instead of the d'oraita 4 fl. oz. (119 ml) (which is required for kiddushes for Shabbat evening and all first-night Jewish festivals).

• Morning kiddush requires a halachically legal “meal” with these elements:
  • Blessing on a minimum of 3.3 fl. oz. (99 ml) of wine (or other beverage),
  • Someone's drinking at least half the beverage, followed by
  • Eating at least 1.3 fl. oz. (39 ml, or 1/6 cup) of some type of mezonot within four minutes. 
    Note If you drink at least 3.3 fl. oz. (99 ml) of wine within 30 seconds, you do not need to eat mezonot.
    Note You do not need to drink the wine or other kiddush beverage to fulfill “establishing a meal.” You may hear kiddush and then simply eat the required amount of bread or mezonot. This applies to Shabbat or Jewish festivals, evening or morning.
     

 

• The real meal (kovei'a se'uda) requires eating at least 1.9 fl. oz. (56 ml) of bread (or matza during Passover!) within four minutes. It must include enough food to satiate. 
  Note You can simultaneously fulfill the requirement to “establish a meal” and to “eat a meal” by eating one (the same) piece of bread.

Don't say ha'gomel for anyone other than yourself (not even for your spouse or children). Likewise, one person may not exempt the entire congregation for ha'gomel except b'di'avad.  But when an entire congregation says ha'gomel, use “gemalanu.”