I am always going to be team education for my brides. Before you book with a vendor at your wedding you want to have a consultation with them. You want to make sure you mesh. The worst thing is having a vendor you aren't compatible with. Here are questions you should be asking during your consultation
What package options do you offer?
Do you have a contract to protect us both?
Can I see your references/reviews?
Are there any change fees?
What are your emergency plans?
Do you subcontract other vendors?
What is your payment schedule?
Are you open to creating a custom package?
Do you do a final meeting prior to the wedding date?
What kind of communication do you prefer?
Each of these questions can be asked and should be answered quickly by a vendor. Whatever the vendor is they should have these things figured out for their clients. It allows you to get to know their business better and helps you determine if you want to work with them.
Red Flags should be flying with the following: no contract; don't give someone money without a signed contract. The contract protects you and the vendor. No emergency plans; in the event of an emergency they should have a plan in place to ensure you are taken care of on your wedding day.