To create a coupon for use only by first-time customers, create a new customer type called "New Customer". Then, when creating your coupon, be sure to:
*set usability for the coupon to only the "New Customer" customer type (Coupons / New / Usability).
* set the coupon to be usable only one time per customer (Coupons / New / Customer Usage Limit), and
*set up a customer type upgrade on that coupon (Coupons / New / Customer Type Upgrade), and
This is recommended ONLY if you do not otherwise utilize customer types for experiential differentiation by customer type, such as for pricing, product visibility, club membership, taxability, shipping methods, etc.
Be sure to turn on customer type history tracking if you create this type of coupon.