If you have watched an engaging movie or web series, you will notice that the opening scene is quite interesting to keep you hooked till the end. Similarly, the essays that you write for the UPSC exam should be of the same format.
Writing good essays is an art that all UPSC candidates need to master. To do this, candidates can appear in several essay test series conducted by different UPSC coaching centers online.
http://www.ekademia.pl/blog/iascoachingelite/how-to-write-the-introduction-of-upsc-essays