The first thing one should do is know your personality:
1) Write down your reactions to different situations in past.
2) Take feednacks from people or recollect given feedbacks by your family and work circle.
3) Check your satisfaction on the picture which points 1 and points 2 create of yourself.
4) If not satisfied then decide what you want from yourself and what would that behaviour or personality would get you in life.
5) Then jot down points which you need to improve.
6) Seek professional help.
Every personality one wants to become is already having seed inside us and we only have to decide select the seed and nurture it.