Hey, that's a very common challenge.
Here are some tips I have been taught in my theater degree :
Have a good script and be confident with it.
Mark where the beats are in the script (natural breaks in ideas)
Use the spots to pause and observe audience so you can react appropriately
On your script, underline the lines that you want to speak quickly and which ones you want to speak slowly. Also mark volume increases/decreases.
Breathe
Practice practice practice
