Practice makes perfect. You know how to use your tool, you are good at it, you know when to use it and when not to. Yet, when the time will come you will fail because you have not practiced often.
The difficult part about being a manager today is that at office you are expected to be a great communicator and give presentations after presentations. But in school and college there is hardly any formal education that is imparted to make you a better presenter. This is a skill you learn on the job.
How can you practice and become better?
Take initiative and make presentations. If one member of your team is supposed to make a presentation, volunteer to do so and seize the initiative. I am sure that 4 in a group of 5 will happily back out if one of them is eager to deliver the talk.