A serial dilution is a step-wise and geometric series of dilutions which starts with a small amount of starting material and amplifies the dilution factor serially by using diluted material as a source for subsequent dilutions.
Serial two-fold and ten-fold dilutions are commonly used to titer antibodies or prepare diluted analytes (for a standard curve for example). Serial dilutions are also commonly used to avoid having to pipette very small volumes (1-10 µl) to make a dilution of a solution. Serial dilutions can be performed in tubes (microfuge or 12 X 75 mm) or in the wells of plates (depending on the volumes you require). It is important to know what volume of the dilution you will need and the range of concentrations that you desire.