USA L1 Visa is the visa which is used for employees being transferred to America from anywhere in the world. You need to be prepared with your documentation when you are going for the interview. You should be well aware of the company details in which you are working. Another important aspect is because this is a business visa you need to know perfectly about what your business deals with and what your role is in the whole program. If you do not have an idea about this point then it is better if you brush up your skills before attending the interview.
Never be under the misconception that your application is rejected due to the mood of the officer at USCIS. This is not at all true. The officers are trained officials who know how to deal with various moods. They interview millions of people around the year which gives them enormous experience various applications. It is very important for you to behave yourself and provide genuine information and give modest answers to the officer to whatever queries he has to ask you.