If you are a beginner, the most effective way is with a good class or a teacher. If you already know the basics of the language, you can do a lot with a good self-study book. There are also a lot of internet sites that present the grammar topics and then give you some exercises to practice. Usually the books present the topics so one topic builds upon the previous topic. If you study alone, you will need to figure out which topics to study in which order. It's not a good idea to study indirect speech, for example, if you don't know how to form the simple past tense. And to be most effective, you should also have some opportunities to USE the grammar in conversations, oral presentations, etc.

how I can improve my english grammer in an effective manner ??? i think you should say "how can i improve my english grammar in an effective way/manner?" my suggestion: you can try to learn the grammar in daily english learning,when you read a sentence you should see what kind of grammar in it. you can realy know how to use the grammar in english when you read more.

Use a good grammar book and study it with the help of a teacher or an upper-intermediate/advanced English student.

Hi Vivek, this Italki site will help you with grammar http://www.italki.com/knowledge/page/ENGLISH%20GRAMMAR.htm