Devotion is the key ingredient in offering prasadam. There are many methods of self-realization, but Lord Krishna is most pleased by devotional service. We should offer to food to Krishna out of love and affection for Him.
Material nature is divided into three different modes, namely the modes of goodness, passion and ignorance. The Vedas divide food into these categories as well, so when preparing prasadam for Lord Krishna, we only offer foods in the mode of goodness, or satvic foods. These foods are strictly vegetarian, meaning they have no traces of meat, fish or eggs. A few other items such as garlic, onions, and any foods containing stimulants such as caffeine are also prohibited. Lord Krishna is also known as Govinda, meaning one who gives protection and pleasure to cows. Milk products and sweets are some of Krishna’s favorite foods.
When preparing prasadam, we should make sure our cooking area is very clean. Food should be prepared on cookware that is especially reserved for Krishna in a kitchen that is not contaminated by meat, fish, or eggs. When the food has finished cooking, we should arrange portions on a plate specifically reserved for prasadam. No one else should eat off of this plate. We should think of Lord Krishna as the primary guest in our house, and thus He should be the first one to taste the food. Except for testing to see if the food was prepared properly, we should avoid tasting the food prior to offering it.
Once Krishna’s plate is arranged with food, we take the plate and offer it on an alter or in front of a picture or deity of the Lord and chant the Maha-mantra:
“Hare Krishna, Hare Krishna, Krishna Krishna, Hare Hare, Hare Rama Hare Rama, Rama Rama, Hare Hare”
For further advanced devotees, there are several other mantras that can be repeated which offer the food to the spiritual master, who in turn offers it to Krishna.
After repeating the mantras, we leave the altar area and let Krishna partake of the food by Himself. After a few minutes, we remove the plate from the altar. Our entire preparation has now become prasadam and it can be eaten and distributed.
Here are pictures of examples of altars: