In such a competition, where there are million of e commerce sites,what exactly could be done to stand different among so many sites and make a different place? any tips and tactics?
Sorry, but that's far too vague a question. There is a huge range of e-commerce sites in different business sectors, using different tactics and techniques to attract customers, depending on their niche.
I suggest you read the sticky threads and do a search of the forums to get some general information. If you then have a specific question which remains unanswered, please feel free to post again. Meanwhile, thread closed.