You can also jot down pointers from the topics that you go through for revision purposes. Do not overburden yourself with going through irrelevant study materials. Consult your seniors and teachers before buying any material for preparation. While preparing for the civil services exams, the quality of what you read should be given equal importance compared to how much you read. There are various institutes and coaching center that offer coaching for preparation. However, the internet also provides lots of comprehensive options that offer UPSC notes.