Use Mechanical Pencil as Stylus

Generally, most stylus devices are made from some kind of plastic, and plastic is non-conductive. While a stylus works for a Resistive screen (anything that applies pressure allows the hardware to track where that pressure occurs), most stylus will not work on a capacitive screen because touching the screen with a non-conductor like plastic doesn't change the electrical capacitance of the screen.

This is also why you can swipe your finger along your iOS device and cause it to do something but if you put your hand under your shirt and try the same thing it won't work. Even something like a metal pen won't work becuase it doesn't create enough of a connection on the screen.