Drilling a water well is different in many areas. Some areas have abundant water underground while others do not. In some areas it is very deep to water, while in other areas water is shallow. Wells can be drilled through sand, clay, rock, or granite. Water can be found just about anywhere you drill in certain areas. In other areas you have to be exactly in the right spot, and in even different areas there may be no underground water at all.
Some drillers will use PCV casing, while the formation dictates that other areas require steel casing. Small diameter casing is used in some parts of the country, while in other areas larger casing is required
All these things combined make it beneficial to use the expertise of a local driller. Drillers in your area will be familiar with the formation and the amount of water you can expect. Some drillers will have the experience to be able to guarantee water at your location. Other areas the driller may have no idea about the performance of a well in your location, until the well is drilled.
I recommend larger diameter casing. Larger casing will give you more options of pumps available. Larger casing is also less likely to let the pump get stuck in the well.
Once the well is drilled, a pump test should be done to determine the rate of production, well storage capacity, and/or the recovery rate. With this information you can determine the size of pump required and whether or not additional storage is needed.
An experienced local well driller can be a wealth of information and save you time and money. A reputable well driller will be glad to furnish a list of references for you to check with. The best way to verify the ability of the well driller, is to talk to several people who he has drilled for in the past.