Whether or not you move forward with a project request, it is always a good idea to hold onto their information. When you are viewing the details of a request, take a moment to look at the name.
If the contact is already in your customer database, the name is a hyperlink that takes you right to their customer record.
If the name does not have a link, this is a new client. Use the Create Customer action at the top of the page to add them to your database.