Question: how to make x gal plates?
Answer: Add 10 µl. ... 
Add 10 µl IPTG (100mM) per 1 mL of Media for a final concentration of 1mM. ... 
Add screening antibiotic of choice (Ampicillin, Kanamycin, Carbenicillin, etc). ... 
Pour plates and allow to cool to room temperature (usually at least 30 minutes) before use.