Exactly in which year should I start preparing and applying for GRE, TOEFL and IELTS for MS in US? how & where,any good classes to join for?

WHILE YOU ARE IN FINAL YEAR OF GRADUATION OR POST GRADUATION YOU CAN PREPARE FOR IT

IELTS is valid only for two years. Hence you do it while you do your final year. When you do IELTS you need not do TOEFL GRE only if the university you apply for is asking for you do it. Otherwise it is not necessary.