You can use the volume keys as a shutter button.
Trying to take pictures with one hand using the default shutter button could prove to be hard, especially if your phone is bigger. It could make the picture you took look a little shaken or in worse cases, you might even drop the phone. So, if you want to take one-handed pictures, this is the way to go.
Only use a dry cloth, or in extreme circumstances a lightly moist cloth.