Well, first things first: If you are getting significant refund, let’s say over $2,500, you might want to reevaluate your withholding on your weekly or biweekly paystub. You may be paying too much in taxes over the course of the year, which results in your big refund when you file. In essence, you are providing the government an interest-free loan. One year I got a whopper of a refund, and then worked with UBS payroll department in Human Resources to reduce the amount withheld from my pay every 15th and 30th of the month.
But when you get that money back, what should you do with it? I would advise an allocation like: 50% pay down debt; 20% save; 20% invest; 10% enjoy. Exact allocations can vary in individual circumstances, but the main idea is to decide to be responsible with the vast bulk of it, while still allowing a little fun on the side.
Enjoy and best of luck.