What is fasting? How is it done? In other words, is it strictly no food or water? Is there more than one way to fast?
In the strict halachic sense, fasting means not intaking any food or drink, from the time of dawn (alos hashachar) until night. In addition, the fast must be ‘accepted’ before sunset of the previous day. In other words, for a full halachic fast to apply on Monday, one must accept the fast upon himself on Sunday before sunset, and then refrain from eating or drinking from dawn of Monday until Monday night. Having accepted the fast, this fast would also be obligatory, due to a ‘vow’ that is accepted.
Some mention other forms of fasting. An example is fasting from speaking (meaning, accepting upon oneself not to speak any word other than Torah study, for a specific period of time). Another is known in the name of Raavad, who suggests a form of fasting in not completing a meal entirely, and refraining from finishing the food.
It is possible, however, for a person to do other combinations of fasting. Although they do not have the status of a halachic fast, if they aid a person to focus on his spirituality, and bring him closer to G-d, then his intention and deeds will surely be rewarded.