I am at present in my 1st year. From when should I start my gate preparation and is coaching necessary ? Which books should I refer, and how should I prepare ?

The syllabus of GATE exam is designed such that it covers one or two subjects of each semester of graduation courses. In first year, you may focus on general aptitude and engineering mathematics. Later, in next semesters you must give an extra attention to those subjects which is included in GATE syllabus. Meanwhile studying the subjects for your semester exams, keep solving GATE level objective problems. Never forget to revise the subjects previously studied. Coaching can help you in scheduling your course structure and keep you stable towards your goal. But, If you can go in the above mentioned way of self study, it is not required to join any coaching. In market, lots of GATE books are available. For theory, you should always refer standard text books. For practicing problems, go for those books which is completely solved; it will be helpful in clearing your doubts and building your concepts.