Hi Kalyan,
Your question is too broad to answer in a forum post. The skill of Performance Tuning is very complicated because there are so many different technologies and data involved in even a simple transaction.
But I'll offer one general piece of advice. The overall way to think about performance tuning is to "divide and conquer": Break down the slow transaction into pieces and run it 100 times while taking timings of each piece. Take measurements of a good transaction, too, so you have something to compare against. Now identify the slow pieces and break them down! Keep drilling down into the work until you find an unresponsive system or a slow SQL update or an HTML request with 300 huge gifs or a full queue or....
Good luck.
Jeff