Research prior to your interview
You will be given a full training before starting your job at any banking institution. However, it is still a good idea to learn something about services and products of this bank before an interview. You should at least browse a website of the institution for an hour or two, to get a good grasp of their portfolio, as well as to investigate the latest trends and news in the industry. Once you have this knowledge, you can use it very effectively in role play exercises.
For example, in a typical role play exercise, you are supposed to sell a credit card. If you know something about its benefits and specifications, you can use it to your advantage. Any interviewer at the bank would give you positive points for such an application of practical knowledge in a role play.

How to answer behavioral questions in an interview 
Answers to behavioral questions can sometimes decide a winner in an interview. Interviewers ask you about your behavior in various work-related situations from the past, to forecast what you would do in similar situations that happen in banks on daily basis. Let’s have a look at one question:  
“Give an example of you dealing with an irate customer and what you did to fix the
problem?”
Many times, I heard applicants reply to this question:  
- I do not have such an experience.
- This is my first job application for any customer service job .  
- I have never been in that situation.   
All of these answers were really bad. Candidates could hardly get any positive points for their answers because they did not answer my question at all...

Question: Tell me something about yourself 
Hint: Interviewers are not interested in your family, or in your free time activities (many job seekers talk about these things). You should focus more on your personality, experience, education and professional interests. On the other hand, it is fine to present your outgoing and honest personality, mentioning some of your hobbies or personal interest. This is only a warm-up question, so I suggest you use a short answer.
Sample answers: I am twenty years old, like to spend time with all kind of people and socialize. I am keen to learn more about the banking industry and finance in general. I graduated from high school in this city, with good marks. In my free time, I like to play sports, learn something new and spend time with my friends.  

Why did you choose our bank? 
Hint: You should focus on personal preferences to the institution where you apply for the job, or the vision and culture of a bank of your choice. You should simply focus on something that distinguishes it from other competitors, something what hiring managers are proud of.
Interviewers are not stupid. They understand that a job seeker would be happy to get a teller job in any bank. However, you should do your best to convince them that their banking institution is a first choice for you. 
Sample Answers: I fulfill all the requirements and believe that I fit the company culture pretty well, from what I have observed as a client of this bank. That’s why I prefer to work at this Bank, and not anywhere else. I submitted applications to two other banks also, but I would accept a job here immediately.