Rodney Larmand, President at College Pro, explains how to answer the question:

Where do you think you need the most development?"
Asking a candidate about their strengths and weaknesses in an interview is a typical approach and highly effective. This question can reveal the candidate's insight into past experience, their research on the position, and their willingness to develop within the company.
The common pitfall when answering this question is claiming that your weaknesses are also your strengths. For example, `My strength is that I am detail oriented. It is also my weakness because some tasks take me longer to complete.' This does not say enough about the candidate to the employer and appears less genuine.
The other common pitfall is not using specific examples or referencing details about the company you are applying for. A strengths-and-weaknesses question is an opportunity to showcase an understanding about the company, including where you can fit in the picture. An employer is looking for someone they want to work with and fits into the company culture.
Understanding where you can improve demonstrates insight from the candidate. Use specific details about the company: the people, projects, and positions that apply to areas of interest for the future.
The first step when preparing for this question is to write your answers down before the interview. Try to anticipate other common interview questions you've heard before. Keep your answers between 40 to 65 words and practice verbally.
For example, to answer the question ' what experience can you contribute to this position and where do you think you need the most development? ' you could say the following:
I have four years of experience working in the field of sales. Based on my understanding of the training program here, including the sessions on selling, I feel I can benefit from the personal assistance of a General Manager. Although I was effective in generating interest from prospective clients, I believe I can improve my efficiency to achieve better results.
Know as much about the company and the interviewer as possible before the interview. This means researching the company's website, Twitter, Facebook page, newspaper articles, parent companies, partners, and the career path of employees. 
Once you have an understanding of the company, be clear on your experience. Understand the results you've produced, and the accomplishments you've made. When asked a question, provide concrete examples to illustrate your point.
Every question is an opportunity to communicate your fit for the position. My advice is to be clear, honest, concise, and prepared.