Network! This is important not only for making the most out of the internship itself, but also for return offers! It's super helpful for your recruiter if other people in the office know you and can vouch for you. Also, it's important to keep asking for work, which can be an excellent way to network - if you're ever bored, you're doing something wrong. Asking for work can also expose you to areas of the bank you wouldn't interact with otherwise, which is really important, especially when it comes to evaluating your long-time career path.