What is the format for a character certificate for admission in DU issued from a gazetted officer? Should I take a printout of it or manually write it?

The character certificate is issued by the most recent institute you attended, in this case, your school. You should visit your school and request the administration a character certificate for yourself. 

The school is responsible for making sure that you get your character certificate. It would be suggestive that you collect all the original documents from the school along with the character certificate.