you should always do a minimum killing assay to find out the minimum concentration of puromycin to kill all the cells.
From my personal experience, epithelial cells are very sensitive to puromycin, and i used only 0.5ug/ml of puromycin to kill all my epithelial cell lines. For many other cell lines, i have seen 1-10ug/ml of puromycin being used.
I would suggest you set up a preliminary assay to test the 0/5. 1, 2, 4, 6, 10 ug/ml of puromycin to find out the minimum concentraion to use in your cell line.