Ammonium sulfate you say right? Anyhow, that depends on your protein. If it is more hydrophilic it will require a larger amount of salt, if it is more hydrophobic it will be less. You need to conduct experiments if this information is not already known for your protein.
Ammonium sulfate precipitation can be used as a first fractionation step in soluble protein purification. The salt concentration is increased in stages by adding the solid salt gradually with mixing, allowing some time to pass, then centrifuging after each step. More salt is added to the supernatant at each stage. Each pellet is resuspended in buffer and tested for the presence of the protein. The following paper provides tables for ammonium sulfate addition. Concentrations used are in the molar range.