Prepare for JEE Advanced besides JEE Main through the 2-3 years of your Preparation. When you appear for JEE Main ensure your Performance exceeds the threshold or Cutoff for JEE Main, hence making you eligible for appearing in the JEE Advanced. Ideally, most of the IITians have a Score much higher than the Threshold Category Cutoff in JEE Main, which Category they belong to.

For more information about JEE Main cutoff do follow the link below

https://engineering.careers360.com/articles/jee-main-cutoff

Hence, when you appear for JEE Advanced, incase your are from OBC/General Category, target anywhere above 30-35% of the Total Score in Paper and confirm your Seat in IIT. Whichever Category you belong to you should take references from the Previous Years, at which Last Ranks, you secure a seat in IIT, which varies each year, besides clearing the General JEE Advanced Cutoff.

For more information about JEE Advanced Cutoff do follow the link below

https://engineering.careers360.com/articles/jee-advanced-cutoff/amp