Now that we have examined the hardware and its manufacturers, we are ready to cover some of the tips and techniques that are useful when working with touch screens.
Keep an eye on your angle of attack. Certain touch screens are actually sensitive to the angle at which they are touched. This is not a physical item, but actually an optical illusion. SAW (Surface Acoustic Wave)-based screens with their extra glass layer, depending on its thickness, can fool the eye slightly during calibration. Typically, targets are presented during calibration for you to press with your finger or stylus. Even the tiny difference a small sheet of glass over the screen makes can sometimes throw off a person visually as they go to click on the targets and calibrate the screen, depending upon the angle at which you are viewing the screen. So standardize the viewing height at which your screen will be calibrated and presented. An extraordinarily tall person will see the screen at a different angle than a person of average height and this may be just enough to throw her finger aim off by one-quarter of an inch and thus make navigation with small buttons more difficult. Even a left-handed person may have a slightly different touch angle to her finger than a right-handed person. Try your input, as both a left-handed and right-handed individual. It wouldn't hurt to try using your knuckles and thumbs as well if your application is geared toward children.
Don't forget the environment. If your application might be deployed in an area where the temperature can get very chilly, consider that your users may be gloved when they attempt to use the touch screen. In this case, you should also allow extra room between the buttons. The type of screen you use is also a factor here as some of the technologies mentioned here are better suited for gloved operations. Resistive technology based screens and SAW screens are ideal for this, whereas capacitive-based screens are not.
Determine the screen real estate you need. Do some tests and see at what resolution you need to run your application. Will 640x480 be enough? Is 800x600 enough real estate for all your content or will you need to go higher? This may dictate the type of display you purchase or deploy on. If you are using a standalone player or projector you should build your application at a size that will allow scaling to fill the entire screen, so be sure your document can scale proportionally to fill the screen. Because the resolution you need will affect your purchasing decisions, it is a good idea to tackle this question early in the planning stages of your project.