You need to check the details of company, you need to know what type of business they are into, first try to understand the company background thoroughly.Credit: Unsplash
This document you will find in SEBI website, it is a prospectus filed by the company, this documents consists business details, financials and promoters.
Understanding the background of promoters is a very important factor, because company's management will be responsible to drive the progress of the company
You can get to know this by reading Red Herring Prospectus, see what they are good at, check the overall growth of company from past years.
GMP means Grey Market Premium, you will get to know this after the IPO is issued.