You should check the following article.

Link:

You can follow below points for your preparation

-Understand the syllabus for the exam. 

To prepare GUJCET you should prefer GSEB books. It will help you to clear your concept. Here are some of the preparation tips you can prefer.

1. Focus on your 12th Examinations and performance.
2. Clear concepts according GUJCET Syllabus and prepare from textbook of GSHSEB.
3. You must read and remember all formulas of Maths , Physics and Chemistry.
4. Solve Mcqs from Textbook and small easy examples and sums.
5. After You have to take question bank(Swaadhyayanpothi) of Physics, Chemistry and Maths.
6. Start solve portion of one mark Mcqs .(Don't remember the answer because they ask similar question and you answered it in wrong way )
7. After solve your query related topics and discuss with your teachers.
8. You need just maintain your time what you have after routine .
9. You should pay minimum 3 hours of day to solve Mcqs and try to maintain your speed of solving it.

Good Luck!