You should follow below points to start your preparation-

1. Internalize the GATE syllabus: Before diving in, you need to know what is in the pool. So, go through the official syllabus of GATE 2018. It will give you a clear idea regarding the topics you need to study for the entrance exam. General Aptitude (GA) is a mandatory section for all GATE papers. Meanwhile, Engineering Mathematics is compulsory for all papers except (GG & XL). The syllabus has many other key details that would help you streamline your focus.

2. Check the GATE 2018 Exam Pattern: The exam pattern of GATE 2018 will give candidates hints on how they should prepare for the exam. For instance, two types of questions will be asked in GATE 2018: MCQs and numerical answer type (NAT) questions. Also, MCQs carry negative marking, while for NAT questions no marks will be deducted for wrong attempts. All similar points outlined in the exam pattern of GATE 2018 has to be taken special note of. Remember, every extra mark you earn is going to count.

3.Study material: You can check below recommended books for your preparation by below link

GATE Study Material

4.Take notes: You can make your important notes it will help you in revision.

5. Focus on speed and accuracy: Speed and accuracy are key elements for success in GATE 2018 and go hand in hand. When solving a problem, see to it that you are picking up speed. One way of increasing speed is clearing concepts and remembering all important formulas.

6. Solve Sample Papers: You should also solve sample papers for your practice and to analyze your preparation level and to know your strong and weak areas.

7. Revision: Focus on revision as it is important part to score good marks.

Good Luck!!

This is very good to know that you are so serious about your Gate preparation but as per my view it is better to start your preparation in your 3rd year because first 2 years of B.Tech is the ideal time to make all your basics concept clear and strong. Apart from this, below I am providing Gate preparation tips which you should keep in your mind whenever you start your preparation  -
1. Know the syllabus very well.
2. Read standard books only as there are many books available in the market so it is advisable to use the books which make all your concepts clear and which are easy to understand.
3. Understand the weightage of topics properly.
4. Proper Revision plan should be followed.
5. Mock Tests and Practice Tests should be done as this will help you to learn time management skills and this will also make you familiar with the exam pattern.

Hope this helps!!!