Two Job Interviews

Okay so I am currently employed, but haven't worked since August because I left for college and they still want me for the holidays and honestly, I don't want to work there anymore from how bad they treat their employees and how cashier's get the backlash from the customer's. So I applied to jobs (at the closest mall) that are closer to me while I am at college, I got called from Clark's and I have an interview at 1pm on the 9th and then I just received another call from Tilly's for am interview at 4pm, so now I have two interviews in one day, both at the same mall. How do I decided which job to go for? Do I tell the employers that I have another job offer? What if both jobs hire me, how do I turn one of the down if the other is better fit for me? I've never been in this situation and not sure if I am asking all the questions, help, please?!