How can you enter a classroom sit down in seat and notice if someone sat there the previous class?

Look to see if the chair you are about to sit in is pushed in or pulled out. If the chair is pushed in, it is likely someone sat there in the last class. If the chair is pulled out, it is possible that no one sat there in the last class.

Check to see if there are any personal belongings in the desk or chair area. If there are no belongings, it is likely no one sat there in the last class. If there are belongings, it is possible that someone sat there in the last class.

Look around and note if you notice anything unusual or different about your seat. If you see anything that seems out of place, it is possible someone was there in the last class.

Ask a classmate or the professor if they know who was sitting in your seat during the last class. This is the most direct way to find out if someone was there in the last class.