Trim away some of the excess branches with pruning shears before transplanting or moving a forsythia, to ensure there is energy for root growth later. Provide some extra water two or three days before moving it.
Dig deeply around the root system of the plant, creating a trench around it with a shovel. Larger specimens require that the trench be further out due to their more extensive root system.
Dig under the root system, doing your best to avoid severing the tap root. The forsythia's tap root generally reaches straight down among a mass of fibrous roots. Sometimes, cutting part of the taproot off is impossible to avoid. The fine roots that make up much of the root system will keep the forsythia alive if this is the case.
Carefully remove the root system from the ground. Lift the tap root from below to avoid tearing it out of the soil, which could break it more than desired. Do not shake soil from the roots as this can also break the roots.