You should also be aware of shirt sizes when you order.... Of course not knowing who you will get presents a problem when trying to order a shirt to fit her! And how embarrassing would it be if you pledged a fluffier lady and only had small shirts. We generally do it by percentages of who is in the chapter now. For example, we have 65 active members - 60 order smalls and 5 order mediums. We always get 35 of everything for our new members, and for tshirts we are getting 32 smalls and 3 mediums which is somewhat on the same scale of our current membership. I like to throw in a large as well, just because you never know.... If we wind up not using it, there's always an advisor or someone who will want to buy it and put a little money back into the budget.
Of course these are unisex shirts - NOT fitted. Keep that in mind as well. Ask your tshirt company to send a sample of a small, medium, large, x-large so that everyone can determine what will fit them. Depending on the company and how much business you do with them, they'll send them free of charge or calculate the cost of the samples into your final bill. Don't forget to check with local businesses too! We use a local guy for everything so he pretty much sends us whatever we want for free cause we've built up the goodwill. (Plus his prices blow everyone else out of the water and we don't have to pay shipping!!) It's always good to keep your money in the local economy!
In the event that you haven't ordered enough shirts for everyone (which happened to us 3 years ago), ask for volunteers amongst your membership to allow a new member to wear her shirt until more can be ordered. Then be sure those members wear the same color shirt so they don't stick out in the pictures! You don't want to risk alienating a new member on her first day by saying "sorry, we didn't order enough, and YOU are the unlucky one!"