Clay can be incised to create pottery decorations. Various incising tools will give differing incised lines. Tools vary from old pencils to steel tools made just for potters. Try out a variety of tools and pointed objects to find the ones that you like best.
Incised work can be done when the clay is wet, for softer lines, or at medium to stiff leather-hard for sharper-edged lines. Do not attempt to brush away any curls or fragments of clay; they will tend to weld back onto the clay surface. Instead, either use a soft, dry brush to flick them away, or wait until the pot is bone dry, at which point they are easy to dust off.