Most often professors and teachers do engage teaching assistants to help out in the class. In such cases it becomes important that both you and the assistant are in sync with each other and on the same wavelength so that both of you know what is required to be done so that the pupils are benefited.
As the teacher you should always remember that you are in charge of the class and the responsibility lies with you. If your assistant messes up, it reflects on you. The assistant is only supposed to be your aid and work under your guidance and directions. She will not be equipped to take over as a teacher at any point of time.
It takes a while for both the teacher and the assistant to work together in tandem. After starting to work for a few days each one gets to know the other better and recognize the strength and weaknesses and team up together.
You can include your assistant and work together in preparing the plan, the lessons as well as the assignments and projects so that there is no gap in communication.
You can assign some individual responsibilities to the assistant once she gets a grip on things so that you are able to share the work load too.
As a normal routine it is better for you to discuss your teaching methodology and go through the rehearsals with your assistant well in advance so that you both are well prepared before you start off. After the class is over it helps to go through with a review and see what can be improved. It is always a must to appreciate and respect your assistant especially to set an example to the students too.
Always remember your students are watching you. When you appreciate and respect your assistant, they too will do the same.
As a good teacher you should always be open to suggestions and invite your assistant to participate with her own ideas and bring about new changes too.
You should always remember to give assignments to your assistant in small bits and pieces and do not over load him or her. If they fail to deliver as per expectations then it will be your failure too and doesn’t help the class at all.