If the stock antibody (purified) concentration is 1 mg/ml, you can do 1:100, 1:200, 1:500 and 1:1000 dilutions.

Thanks , I am askinhbgor routine work in diagnosis of leukemia gor example

You need to pick up the concentration of antibody which differentiates the positive samples from negative or unstained samples better. Goodluck

The antibody concentration needs to standardisation before use. So you have to check flow cytometry data, different dilution of m Antibody (ranging from 1:50 to 1:500), select one dilution of the antibody which works best for the cell. If you bought it from any company, just check in manual given with antibody (they have sure mentioned about dilution best for western, confocal imaging and for flow cytometry also, If not then just use the dilution mention for imaging. 

What I have seen 1:100 dilution works best. Best of luck....