hello...I am preparing for neet 2018 please advise me good strategy to study and score 550+ marks?

Aim above 600 plus though it can be difficult but not unachievable.
You have enough time and so know about the exam very well. Like the eligibility, syllabus etc.

It may sound common but the fact is making a study table is quite useful and make it in slots. Set your routine in a way that you target the difficult ones first and then go to the ones you can handle well.

Prepare well, master with basics, keep revising.
Side by side keep giving online/offline mocks.
Work on your strengths and weaknesses.

It is important to analyse your performances weekly atleast.

You can follow below books for your preparations:

Best Biology Books for AIPMT/NEET Preparation:

NCERT Biology of Class XI and XII
Trueman's Biology Vol 1 and 2
Objective Biology by Dinesh
Pradeep Publication's Biology
GRB Bathla's Publication's for Biology
Best Physics Books for AIPMT/NEET Preparation:

Concepts of Physics by H. C. Verma
NCERT- Physics Part 1 and Part 2
D C Pandey Objective Physics
Fundamentals of Physics by Halliday, Resnick and Walker
Problems in General Physics by I. E. Irodov
Best Chemistry Books for AIPMT/NEET Preparation:

NCERT Chemistry
Physical Chemistry by O.P. Tandon
Organic Chemistry by Morrison and Boyd for Organic Chemistry
Moderns ABC of Chemistry for class 11th and 12th
Concise Inorganic Chemistry by J. D. Lee for Inorganic Chemistry
Dinesh Chemistry

Good Luck.