I want to start preparation for gate. so plz tell me how can I???

Know GATE Syllabus First
Design Your Study Plan,
Study Standard Books No Need to Buy Read Online,
Solve Sample Papers, Prepare Notes Simultaneously,
Enroll to Online Mock Tests, 
Maintain Consistency
Study in group; help each other to help yourself.
Don't buy too many books, buy some quality books like gateacademy's EE series etc.
Write technical exams, during preparation too one can write these exams.
Manage your time well, memorize formulae and numerical values.
Divide syllabus into sub-topics, allot fix time to each sub-topic, for example, 20 minutes per topic.
Experiment with questions and find new tricks to solve questions. Revise daily.
Good Luck!