Hello aspirant,

As from this year the gate eligibility criteria is changed and the third year students also give the exams now so starting preparation from today for is very necessary.

First of all you will go with the syllabus and the pattern of exam. Then make a good study plan which will help you in cracking gate. While studying you will make notes which will help while revising all the concepts. Revision is the most important thing as only study is not  sufficient revising is also must.

You have to also give the mock tests which will be very beneficial in cracking gate exam.You may go with below article regarding GATE 2021 which also help you.

https://engineering.careers360.com/articles/gate

According your second question the online coaching will be also good option in preparation but you have to choose good online lecture because there are various online coachings available.Best of luck for your career.