I think most people have a horrible first interview so don't feel bad. I think it is important to do a warm first impression and have the entrance of your home clean and welcoming.

I do a bit of small talk when they walk in.
I offer to help them with coats, etc.
Make sure you greet their child if they brought them along. A lot of parents complain that providers spend a lot of attention on the parents and none at the child during interviews. Say hi and ask the child's name and greet them warmly.
I usually lead my clients to my living room and offer a seat, show them the back yard from the window since it is a walk out basement underneath. This also allows them to see the kitchen, some of the toys on the mainfloor and the table with boosters, etc without me actually pointing out everything or having to formally show everything.
Then I ask them to tell me a bit about what they are looking for, when they need care for, what sort of hours, days and ask some questions about the child.
Then I ask them if they would like to come upstairs to see the play room and play areas and nap areas. (My daycare is on the upstairs level).
I take them upstairs and show the nap areas and talk about naps a bit, I show the playroom....again pay attention to the child and ask questions to the parent about what their child likes to do. People love to talk about their children.
I then see what questions they have for me and answer those but keep it more like a conversation and not an interview.
I often interject with info about the daycare myself...how much we go outside, about snacks and lunch, about school pick ups and how we do go outside, funny stories about the kids or talking about crafts we have done.
usually parents will ask about your police check and first aid and if they do I get out my binder and show them while talking to them and I show them our newsletters. I usually don't show a formal menu unless they ask.
I usually leave my daycare handbook with each parent.
I do not send all the application forms to the parent. I used to send each parent with all the application forms and questionnaires and financial contracts but I think that is a waste until you know how serious they are. I find that just giving the handbook answers most of their questions and lets them read through and determine whether you are what they are looking for. If they call or email you back then you can get into the other documentation.