"when should I book my maternity session?"
That's a great question! It's best to get in touch with a maternity photographer EARLY -- about 4 to 10 weeks before you want to step out in front of the camera. This way, you can be sure to get the spot you want and not have to go TOO close to your due date. If for any reason the session has to be rescheduled (someone gets sick, bad weather, etc) you definitely want some wiggle room before your due date.
the best time to hold the maternity session is when you're around 32 to 35 weeks pregnant.
Depending on how you carry the baby, you might need to wait until 35 weeks to really be showing. Or you may prefer to do pictures at 32 weeks (or even sooner) if you started showing really early and don't want to be super pregnant for your session.
"do i have to do my maternity session by myself?"
A maternity session can be something special just for you, or you can bring your partner or children along for pictures. Some moms who come to my for maternity pictures