UPSC is a 3 stage   selection process involving Prelims, Mains and Interview which tests your personality test. Prelims has 2 Papers namely General Studies and CSAT.

General Studies has Current Events, History of India and Indian National Movement, Indian and World Geography, Indian Polity and Governance, Economic and Social Development, Environmental Ecology, Biodiversity and Climate Change and General Science.

CSAT has Comprehension, Interpersonal skills including communication skills, Logical Reasoning and Analytical ability, Decision making and problem solving, General Mental Ability, Basic numeracy and Data Interpretation.

You will need atleast to start preparing ahead of 1- 2 years. 3 Years plan is good to hear.  If you are preparing at home, you need to keep yourself away from distractions and focus on the goal ahead. Gather as much as information as you can on each topic and keep yourself updated. Practise mock test papers. The syllabus of civil service is too vast that you need to set your time table on a weekly basis and then every week attempt atleast one test. Focus on the basic concepts and keep yourself aware and updated of the significant developments at National and International level. Make quick notes. Reading English News Papers might help you with current awareness and General knowledge. Focus on personality and communication skills as it will help you with Interview process.