Sounds like you need a book on giving presentations, public speaking, and consultative selling.
And from my perspective "controlling" your client is not a bad thing...in the sense that you are managing your client expectations. You need to clearly define the scope of the work you will be providing to your client, and clearly and confidently convey this to your client....and get agreement on it. Otherwise, they may be asking you to perform tasks beyond what you should be doing...and once you're in the middle of it you may find yourself having trouble saying no. I think if you focus on managing client expectations upfront, some/much of the nervousness will go away.