Fast for a Religious Occasion

Fasting can be a great experience instead of a test run at starvation if you approach it with the right attitude.

Steps

Prepare yourself physically. Fasting can actually be a cleansing opportunity for the body, but you don't want to make yourself sick. Eat a good meal prior to beginning your fast. Don't gorge yourself, but don't go into it on nothing but a snack-size meal.
Limit your fast appropriately. If there is not a specific limit already set by your religious tradition, limit the fast yourself to 12-24 hours. Anything less is not much of a fast, and anything more could lead to serious physical problems. Remember that your fast should be a good experience, not a dangerous one.
Make the fast an opportunity to step-up your spirituality. Set aside time to study scripture or other inspirational writings, and meditate on their meaning.
Pray before, during and after your fast. Whatever your purpose for religious fasting, it can be a great opportunity for spiritual growth when accompanied by prayer. Pray with purpose, expressing gratitude and articulating both your needs and the needs of others. Pause to reflect and meditate on your prayer and your fast.
Close your fast with prayer. If you were fasting with a specific purpose, take the opportunity again to express your purpose. Express gratitude for the opportunity to fast, and for being able to complete it!

People of many religions fast for different reasons -- Muslims (Ramadan), Jews (Yom Kippur), Christians (Lent), etc.
Remember why you are fasting. When your stomach growls, or you feel hungry or weak, recognize it as an opportunity to remember the purpose of your fast - not a weakness or something to grumble about.
Stay away from food. The sight or smell of food will probably make fasting more difficult physically, and if food is easily accessible, you may subconsciously begin to snack.
Discreetly inform close friends, family, or associates that you are fasting, so they can support you instead of inadvertently undermining your fast by offering food.
When it is time to eat again, start slowly. Your stomach may not be ready for harsh foods.
When fasting, distract yourself from food. If possible, sleep late so you can wake up later and spend fewer waking hours fasting.
Drink lots of water during your fast if you are permitted. Dehydration can be very dangerous, and since your body is not getting the water it normally gets from food, you will need to drink more to make up for it.

Be aware of your body's signals. Hunger and lightheadedness are normal when fasting, but if you start to feel excessively weak or pass out, you may be endangering your health.
If you are taking medications, ask your physician before fasting and continue to take them as instructed by your physician.
Do not fast if you are seriously ill. Don't use a minor illness as an excuse, but consider your own health and the possible risks associated with fasting. Even in some religions, such as Judaism, you are required not to fast if you are pregnant, or such.
If you do not want anyone to know you are fasting, try going out of the workplace for lunch or going into another room when people start to eat.