As you have asked about the tips for cracking GATE without coaching, you can go through following points
You should get a thorough understanding of the complete syllabus: Just go through the syllabus and have an idea about all major portions you need to cover as 90% of GATE syllabus is what you have studied in your graduation. So, recognize what you need to know, what you already know and where do you have to put on extra efforts.

1. Strategize how you are going to prepare that include setting up your own targets and deadlines: Note down the topic/chapter/subject you intend to study say in a week/day. Test yourself to meet the set targets and deadlines. This will keep you interested and ensures you have steady pace while preparing.

2. Solve past year’s papers: As soon as you are confident about the 50 percent of the whole syllabus, start attempting mock test and solve more and more previous year’s papers. This will support you understand the pattern followed in the exam and the type of questions asked. Along with all this, it will also help you evaluate your preparation level.

3. Practice: As said “practice makes the man perfect”; the same applies when you are preparing for your GATE

4. Make notes and keep revising them: They are really helpful once you done with your syllabus and just need to go through summary and important topics of every chapter.

5. Join some test series: Try to join some test series after the conclusion of your syllabus. You can choose either online or offline accessible GATE test series as per your convenience.

6. Develop a habit of checking newspapers: This will effectively help you prepare for your GS as well as English questions.

7. Eat healthy: And, last but not the least, Eat healthy, exercise daily and have appropriate sleep.