Before digging the borewell, it is important that you do some research and ground work. Enquire about borewells in the surrounding sites/area or construction sites. Find out the depth at which the nearby borewells had to be dug to get water and how many inches of water they struck.
Vertical Electrical Sounding is one of the very common geophysical methods used for domestic borewell exploration to locate the best possible area to tentatively dig your borewell. Please note that sufficient open area around the location is needed for conducting the survey. These Geologists charge around Rs.1,500 to INR 5,000/- for their survey and will share the reports.
Local well diviners are known to use wooden sticks or magnetic blocks and are also to some extent successful in identifying borewell sites. But this method may not be always reliable and there is no certainty of water, especially in areas where the geological formation is critical.
For domestic purposes, 4.5 inches and 6 inches diameter borewells are usually drilled. While 4.5 inch is most commonly drilled borewells for domestic purposes as that is the permitted diameter, 6 inch borewells are drilled when higher water load is required for large apartments or buildings. In the initial stages, larger diameter bits are used to place the casing pipes up to the hard rock zone prior to drilling the permitted size of the borewell.
Based on your survey of the surrounding area, you can take a call on the stage to stop drilling after you have struck water. It is also recommended to get the necessary permissions to drill the borewell to avoid any untoward issues with the locals, police. media, etc.