Hello aspirant, 

For gate exam, study of previous questions and their solution is the best way by topic wise.First you have to cover the concept of the topic then problems on the topic are to be done.For previous year question papers, I suggest you books published by made easy Publications because it is less erroneous and it is even used by ACE academy Hyderabad.

Good luck

Hi Aakrati! Careers360 has all the guidelines and preparatory material for GATE 2019. Just what you need is to read the article by Careers360 whose link is given as follows :

https://engineering.careers360.com/articles/how-to-prepare-for-gate

I hope this information has helped you :)