Hello Sakshi, 

You can improve your marks in Biology is the following ways

1. Read your book thoroughly and ahead of time. Dont keep it for the last hour.

2. Take notes of important biology concepts.

3. Revise your notes everyday before going to a lecture.

4. Pay close attention to what your professor says and take notes of it.

5. Ask questions and complete your work on time.

6. Make a study schedule.

7. Avoid cramming sessions. Even studyinf 1 hour daily can help you alot. 

8. Use note cards for quick revision and revise your old materials plus the same days notes.

9. The most basic foundation of biology is that all organisms are composed of some number of cells. Understand this properly.

10. Remember essential molecules.

11. Analyze the traits.

Hope this will help you. All the best.

Hiiii

To improve your biology score stay focused, clear all the basic concepts, do not leave any topics. Stick to NCERT and be thorough with the NCERT. The question paper with made strictly from NCERT. Read line by line and understand every part of it. Purchase some good books which have previous year papers and sample questions. Try to solve these books regularly. Do not waste time schedule your studies and focus more on those topics which have more weightage.
Refer to following links for more help
https://medicine.careers360.com/articles/neet-chapter-wise-weightage-and-important-topics
https://medicine.careers360.com/articles/best-books-for-neet

Hope this helps.
Thanks!!!