This correct answer is in Indian context:
IITs are visited by various tech companies for various kind of tech internships. During the end of the internships most of such interns from IITs get pre-placement offers.
So, pre-placement offers(also called as PPOs) are not obtained at IITs, but they are obtained by interns who are recruited by various tech companies through campus placement of interns, primarily from top-15 Indian engineering colleges.
So, for getting pre-placement offers IIT students should improve their performances at the competitive coding platforms like CodeShef, LeetCode and TopCoder etc. On the basis of such similar coding questions, interns are recruited from various IITs, and later most of such interns are offers PPOs.