The best way to prepare for PhD entrance exams is to study your undergraduate syllabus thoroughly.  

• Make sure you go through all concepts from a basic level and do not leave any topic midway or incomplete.  
• Your aim should be to understand all concepts thoroughly and be able to grasp them even when asked about them in a different way.
• This approach will help you clear GATE easily and give you confidence during interviews as well. 
• To some, the PhD entrance exam is the most intimidating step of the process of joining a PhD course.  
• This is because a lot of things depend on it. The score you get in these exams can determine whether you will be able to pursue your dream research topic or not.  
• Moreover, the authority that conducts these exams determines the cut-off marks based on which they shortlist candidates for interviews.