Hiring a coordinator for your event or wedding is such a personal choice, the reasoning is yours alone. I have clients who have hired me so they don't have to do anything other than show up, some want to work alongside me and then get ready and show up, others want me there just to make sure food stays replenished. When you are going to hire a coordinator it is best if you go in to meeting with them knowing what you would like to see them doing with your event.
Each coordinator has their own set of preferred vendors. They may have worked together on other events and found they work well together. A preferred vendor treats your coordinator well. A vendor who is rude and hard to work with does not make it on this list. Your coordinator may be willing to share recommendations with you and give you access to their favorites. But, remember, they are trusting you to treat their vendors kindly and to help continue relationships with them. When everyone gets along its beautiful.
If your coordinator is setting up a meeting with one of their vendors, please do not ask for a discount. Most will offer one for working with your coordinator.
Your coordinator is going to take all of the information for your event and make sense out of it for them. If they are asking questions it isn't to be nosey, but to make sure they are able to deliver your ideal event to you. Giving them information will give you your dreams. And this also goes with the vendors they recommend to you, your planner isn't going to mention a vendor to you that is out of your budget. Trust your coordinator. They want the best for you.
As a coordinator I wear a lot of hats. I am the keeper of all the information. I talk to every person at your wedding or event, guest or vendor. When I talk to anyone it is as your representative and that requires professionalism. I am asked all the questions.
Being able to respond to someone with respect and grace is the top priority for me. I will always be dressed for the occasion, all in black.
At the end of the day, anything you want your coordinator to do for you needs to be expressed. We don't read your mind, but we will sure try. My goal is to always give more than I am contracted to do. I believe in always under-promising and always over-delivering.