As you are planning to appear in Civil Services Examination 2015, you need to be serious about preparation. As the Exam-Plan is, you need to look at the Preliminary as well as Main Examination related requirement simultaneously.
General Studies is the most important section and is common in both Prelims and Main Examination where it matters a lot.
You need to go through the complete syllabus, and understand the common constituents present in General Studies syllabus in Prelims and Mains.
By adopting integrated approach, commence your preparation with Main Examination oriented study-plan as that almost covers the Preliminary Examination related requirements.
Looking at the recent trends, you need conceptual clarity about the issues and topics you read. For this, NCERT Books are the best resource that helps in building a strong foundation and as you move on, the basic knowledge helps you understand better and your preparation gets real enhancement.
Don’t forget to read newspapers daily. This will improve your understanding about current affairs and contemporary issues that will prove handy while facing this examination.