After complete 12 class then how to prepair for neet exam?

Here are some important tips you can follow for the exam preparation.
Know the syllabus of the examination well :- NEET syllabus is  vast and you need to know the exact location to fish the best output. Cut down on extra information and focus on important topics.
Come up with an effective study plan :- Time is priceless. We all know this, yet many aspirants fail to make the proper use of time. Goal setting can be used as a strategy to help aspirants bring positive changes into their lives.
Work on weaker areas :- It is possible that you are very strong in one subject and weak in the other. Do not get discouraged by the same. Try and work hard more on the weaker areas to strengthen them.
Practice mock test papers :- One of the greatest challenges of the NEET examination is the time limitation. Students have to finish 180 questions in 180 minutes (3 hours).

Positivity is imperative :- Your attitude decides the effectiveness of the learning process. If you possess a negative approach and keep saying that you can’t do it, then this won’t commit to the idea of learning.

You can also prefer the below given article for the further information.

https://medicine.careers360.com/articles/neet-2019

Good Luck!