In most countries, candle lighting time is 18 minutes before sunset. In Jerusalem, many people have the custom of lighting candles 40 minutes before sunset.

You may not light Jewish festival (or Shabbat) candles before plag ha'mincha.  The candles must burn until at least dark (tzeit ha'kochavim) and someone must be there to see the light from the candles after dark.
SITUATION  Mincha minyan begins at plag ha'mincha. You cannot light candles at home and still get to mincha minyan on time.
WHAT TO DO You may light a candle without a blessing, just so you can have a flame for after the festival has begun. You go to synagogue and after ma'ariv you return home and light the candles from the flame which was burning from before sunset. If you will not have a flame burning from before sunset, you must say mincha on your own (anytime from half an hour after mid-day until sunset). You will light candles after plag ha'mincha but before sunset and not join the mincha minyan. Women should skip mincha and light candles either 18 minutes before sunset or have a flame burning from before sunset and light candles from that flame once the festival has begun (but she may not light from a new flame or a match).

Whoever is lighting the Jewish festival candles should have in mind all other people who will be eating dinner in that home.

Like Shabbat candles, Jewish festival candles should be lit only by one person per home. Priority order: wife; then husband; then children.
It is customary for each married woman to light candles on each festival even though she is not eating in her own home and even though her hostess is already lighting candles. She may light her candles at her hostess's house or at her own home (but if at her own home, she must see the candles are burning after dark if she lights there).
Girls should not be encouraged to light Jewish festival candles except when no parent can.
Single people should light Jewish festival candles in their homes if they will eat there.
 

As for Shabbat, Jewish festivals start for women when they light candles or at sunset, whichever is earlier. 
For more details, see Jewish Festivals: Candles: Lighting with Delay until Sunset.
 

Jewish festivals begin for men at sunset or when they say “bar'chu” in ma'ariv, whichever comes first.

A tablecloth should cover the table during Jewish festival meals, but you may remove and switch tablecloths. Even if you have a beautiful and valuable table, you should still cover it for Jewish festival (and Shabbat) meals.

You should spend Shabbat or Jewish festivals with your non-religious Jewish parent (even in a non-religious environment) if he or she wants you to, as long as you can still observe all of the Shabbat or Jewish festival laws AND if your parent needs your help. 

Here are some suggestions (they are NOT halachot!) of what to prepare in advance of Jewish festivals. Add or delete to suit your needs!
  
Candle Lighting

• Check candle lighting time
• Set the candles in their holders (and have matches nearby)

 
Set the Table
Set the table, including the challa and its cover
 
Kitchen Preparation

• Sharpen knives
• Tear paper towels
• Refrigerator: Turn off or unscrew lights; disconnect any LEDs or fans
• Turn on blech, stove, oven, etc., for whatever you will need
• Set up hot water urn
• Turn off stove, oven, if needed

 
Food Preparation

• Thaw frozen meat, fish, and other food that might take hours to defrost before being cooked
• Cook whatever can be cooked ahead of time
• Squeeze lemons; do any other boreir-type preparations
• Chill wine
• Open bottles and cans that will be needed on the Jewish festival

 
Cleaning

• Make beds
• Sweep or vacuum
• Dump garbage

 
Clothing

• Do laundry
• Empty pockets of muktza
• For men, set out Jewish festival talit

 
Muktza
Check that nothing you will need is beneath a muktza item
 
Personal Care

• Cut hair and nails, if needed
• For men, shave or trim beard and mustache, if needed
• Tear dental floss
• Tear toilet paper or put out tissues in bathrooms
• Open any new boxes of tissues

 
Electronics

• Set heat or air conditioning
• Turn on or off lights, or set timers for them
• If desired, turn off or disconnect:

• Alarms 
• Cellphones and phones
• Computers
• Microwave detectors
• Other electronics

You may not grind, grate, or even finely chop or dice food on Jewish festivals. You may not use a garlic press on Jewish festivals.
The minimum size before violating the melacha of tochein varies by the type of food. The resulting pieces must be somewhat larger than the size you would normally use.

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).

Since wool and/or leather was dyed for the Tabernacle in the desert, similar actions are forbidden today on Jewish festivals (and Shabbat). Any action that causes one item or substance to change its color may be forbidden, even if it is not related to dyeing wool or leather.

For when women start Jewish festivals, or more on women's lighting Jewish festival candles, see:

Jewish Festivals: When Women Start: Candle-Lighting or Sunset
Jewish Festivals: Candles: When To Light
Jewish Festivals: Candles: Lighting before Blessing
Jewish Festivals: Mincha Before

 

You should not do laundry on chol ha'moed.

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.