Drinking fluids. & also if that ain't doing muchh for you there are also pills and herbal teas avaliable . Good luck
Theres not much that I know of that you can do until baby is here.
My doc told me to stay extra hydrated with water, eat oatmeal, nipple stimulation after birth helps with production or theres a herbal tea called mothers milk that will help you produce more. Thats all of the tricks I've heard so far but im a ftm so we'll see.
I herd there some kind of pill you can take but im not sure