You also don't want to accept a callback interview with an employer with whom you are sure you would not accept an offer of employment. It is unfair to the employer and other interviewing students to do so. When scheduling a callback interview you want to respond to the employer promptly so that your travel arrangements can be made as cost effectively and conveniently as possible. Make sure you keep a complete calendar so that you don't schedule interviews when you have other commitments such as on-campus interviews, competitions, or exams. Avoid rescheduling interviews, but if you must cancel or reschedule an interview do it as far in advance as possible.
Students often find it advantageous to schedule several interviews in one city at the same time.
It is important to inform the employers about your other interviews so that, together, you can decide on a convenient appointment time and so that the employers can share travel expenses. Guidelines and limits vary among employers. Many students want to schedule callback interviews in conjunction with a visit to see family or a significant other, etc. That is permissible. It is perfectly acceptable to inquire about these arrangements.