More colloquial recipes tend to use phrases such as dashes, pinches and splashes in their recipes, but if you aren't familiar with this terminology and what their measurements, you could end up with a recipe that tastes off.
A dash is equivalent to ⅛ teaspoon, but if you don't want to measure it out, a simple rule of thumb is a quick shake. A pinch is equal to 1/16 of a teaspoon and is about the same as how much you can pick up with a pinching motion. Finally, a splash is equivalent to ⅛ of an ounce. This can also be eyeballed by tipping the bottle until the liquid comes out and immediately stopping.