You need to understand your weakness before you can work on them. And the best way of identifying these weaknesses is to gather feedback from people who knows you. Identify six people who know you in work context and send them an email asking for their help. You may choose colleagues or ex-colleagues, clients or customers, suppliers, or even an ex-boss. Tell these people that you'll greatly value their candid opinions on your strengths and weaknesses in order to help you with your career development. Make it clear to them that you don't simply want compliment and platitudes, but some insight into how you come across to others. Simply these people three questions.

1. What are my strengths?
2. What are my weaknesses?
3. How can I improve on my weaknesses?

Ask people for help in tackling your weaknesses. Trusted colleagues, your manager, or even your friends may have some ideas for now to make you more effective at work. Do you perhaps need training in a particular skill? Or do you just need to behave in a different fashion - perhaps being more assertive, sympathetic, or tactful?? Ask the people that you trust their help and advice on improvement.