Hi Laura,
Do a class activity that gets the students involved in talking, moving about or working in groups. It might be a game or a case study that you used to get them started. This helps to set the stage for the remainder of the class, while you get settled in as the instructor. Develop your lecture to give no more than 5 key points and then examples. This will help you to slow down and it lets you change the pace of the class. If you don't change the pace of the class you will get faster and faster in your delivery until you sound like a chipmunk on steroids. (OK bad example but you get the picture).
When we are nervous we talk faster and faster so by changing pace or doing an activity you create a break that enables you to center yourself and get ready to deliver some more course content.
Move around the classroom as you speak. This is like trying to chew gum and walk at the same time. By positioning yourself in different places around the classroom you again change the flow of your delivery as you move about. These little things all contribute to you being able to slow down and concentrate on effective and efficient instructional delivery.
Gary