IELTS

Its a good thought that you have decided to pursue your Master's abroad. You have lot of things to concentrate on apart from GRE and TOEFL. Because the universities consider your overall profile and give the admit. You have to write GRE exam when you come to the 3rd year of Engineering so that you can fly immediately as soon as you finish your Bachelor's degree. GRE is for 340 marks and its totally online based test. You'll have only Maths and English in the exam. You also need to write two essays before you proceed to the main section, its called Analytical Writing Assessment (AWA). Scores above 310 is considered to be decent provided if you have a strong academic background. Try to score 75%+ in your Bachelor's, if possible present few national or international papers. You can also improve your profile by doing internships and projects. If you are planning for USA then take TOEFL instead of IELTS as some universities in US doesn't accept IELTS score. TOEFL is for 120 marks and it purely judges your ability to Read,Listen,Speak and Write in English. Even it is an online based test.
Overall, If you have 75%+ in Bachelor's with few paper publications, research works, internships or projects, 315+ in GRE and 100+ in TOEFL. Definitely you will get into top universities in USA.
Do remember the competition is at its peak for the Masters program in US
All the best !!!

Theinternational English language testing system(IELTS) is the world's most popular English language proficiency test for higher education and global migration.
The IELTS test is developed by some of the worlds leading experts in language assessment. Ithas an excellent international reputation, and isaccepted by over 9,000 organisations worldwide, including schools, universities, employers,immigration authorities and professional bodies.
IELTS is the most widely accepted English language test that uses a one-on-one speaking test to assess your English communication skills. This means that you are assessed by having a real-life conversation with a real person.This is the most effective and natural way of testing your English conversation skills.