Hello , could please help me with this question?

What variables would you like to add to the model in addition to the ones is already included? What is your criteria would you use to decide witch variable to add?

Note: the model is to predict the daily check-ins on a hotel

the variables that are already in the model are: all holidays and years 2010, 2011, 2012, rates, total rewards, VIP, Free Independent, wholesales, Group and Special Events. Also all days of the week. SuperBoll, Chinese New Year. Dependent variable is checkins. I hope this helps. thank you.