ir is not easy sub.some people say that it is not marks scoring.
i opted this sub for 2 reasons.it proves helpful in current affair second an interesting one.
how to it,dear check the syllabus.the best and comprehensive book for it is by parkash chander.the can cover the theoratical work of ir.
usually questions r current issues based and u have to give the definition of topic,reference from past events and then move towards current issue.
news paper only can make u acquainted with such issues.

preparing of notes is very fruitfull.