First of all you should start with understanding what UPSC is and the exams it conducts and the exam patterns, eligibility criteria, dates, syllabus and all such details.
Next you can decide to take some extra help/guidance from some institution in the form of classroom coaching after your college hours or go for online classes. Online coaching would be a good option if you find it difficult to travel after classhours and would prefer to study from your home/hostel. Apart from the lectures, online coaching provides the students with guidance, study materials and mock tests.
Next set a timetable. This helps in bringing discipline, which is very important when you are preparing for such competitive examinations.
Start reading newspapers, NCERT books from class 6 to 10, Decide on an optional subjectand gather material for it. while preparing make sure to note down important points.
Take regular tests to assess your preparation level and to identify the areas where you need to improve.
NEVER TAKE YOUR HEALTH FOR GRANTED . Get proper sleep, eat healthy food and keep your self hydrated. Ensure that you do not stress your self too much and give enough time to relax and take breaks. Always remember that if you are stressed out then take a break as it would not bring out any good results when you put yourself in more stress.
Following these I am sure you will be able to make India proud one day.