Pick out a day of the week that works for you. Figure out if the meetings will meet weekly, bi-weekly or monthly. Contact members of troop (or their parents) and inform them of the upcoming meeting - include the location and time. Also let them know when the meetings will regularly occur and if you will be collecting dues for future field trips.
Begin prep on your first meeting acitivities. Make sure you include the Girl Scout Promise, Law and Friendship Circle to begin and end the meeting.
Teach the girls the promise and law. Try to incorporate the memorization of at least the promise into the first meeting. I would recommend playing a game to get the girls excited to learn it. After all, they will be saying it at the beginning of every meeting.
Have a snack, if that is part of your budget. It does not have to fill them up, just tide them over until they go home for their next meal. Fruit and veggies are a good idea (if no one is allergic) or do graham crackers and peanut butter if they are easier (or cheaper). Fruit juice or even water is fine for a beverage.
Explain the day's activity through a story book or with the explanation out of the leader book. Make sure you get across the moral and ethical point the activity will pursue; sometimes the girls lose sight of the importance of the meaning of being a Girl Scout and it is important to remind them.
Dive into the activity. Make sure the girls do most of it themselves, only helping if absolutely necessary. This should take most of your allotted time for the meeting.
Form a circle when the activity is complete. This is the Friendship Circle which will be combined with a song and end each meeting.
Reflect on the day's meeting. What went well? What did not go so well? Keep a log or journal to remind yourself of what to do next time or what not to do. Then sit back and relax and start planning your next meeting.