Congrats your close!
My girl had her kittens 2 days ago. It is really hard determining exactly when your girl will go into labor. Signs of milk (colostrum) from nipples come as early as 10 days before labor. Discharge also comes a few days before. The best way to tell when she is in her first stage, is to watch closely for contractions. If you put your hand on her belly and keep it there for a few minutes, during a contraction, it will sort of resemble mountains, belly gets very hard, large bumps. from there, the 1st stage can last up to 15 hours, if her first litter, may take up to 36 hours.
Second stage of labor is when you see her straining, pushing.
Good luck! Kepp us updated when she begins those contractions! very exciting