As mentioned...make it about them and not you. What you can do to make their life easier.
This is helpful if you can find out what their current pain is. What issues are they struggling with? What do they like about their current provider? What do they wish were different.
It would be great if you could get this information before your presentation. That way you have time to formulate your response as to how you can maintain the things they like, and present a plan for dealing with what they don't like or what their pain is.
For instance: Are they most concerned with price? Indoor air quality? Aesthetics - meaning they just want it to look good and they don't care how you get that result? A trustworthy company because their current one is careless or has stolen from them. Do they have a commitment to "green" or environmentally safe products? Does the work need to be done on nights/weekends? Most importantly, and if you can get this out of them, your practially set, "why are you looking to change from your current provider". This will be very telling and let you know how serious they are about making a change. They may say, "We have to put things out to bid every XX amount of years and get 3 bids". Or maybe they unleash a load of concerns about the current provider and then YOU have the opportunity to share with them how you would address those. You get the idea.
If you can't do it ahead of time, then don't think of it as a presentation, but more of a dialogue. When you meet, explain to them that you're company philosophy is to provide the clients you work for a solution to their needs. But in order to do that, you need to understand their needs. Then say ...."I have some questions that I'd like to ask you to determine your needs and if we would be a good fit." And have at it.
The will be blown away, because I bet they never had someone come in and approach it this way. You just differentiated yourself from the others right out of the gate.
Take notes...hopefully you are good at thinking on your feet and can address the things you learned by questioning them on the spot. If you can't or you have one of those "I forgot to say...." after you leave, then you have the opportunity to send them a nice follow up email thanking them for their time and then recapping the main points and you can sneak in that important thing you forgot to say.
Good Luck!
If you need a list of questions, let me know!