I would suggest you practice by attempting the IELTS practice exams from books(names given below). Identify where you are making mistakes, taking more time, whether you are having difficulty because your reading speed is slow or you are having difficulty understanding some grammatical structures.
> If you have problems with comprehension(understanding meaning of sentences, etc).
Refer to a grammar book and learn the relvant sections.
Mark diificult words and learn them.
Improve your vocabulary (book mentioned below).
> If it is because of your reading speed, google for speed reading techniques and use them to see if they help you.
My personal tips:
1. For the given section, quickly read the questions beforehand. That way you know what answers you are looking for.
2. Genrally(and this may vary, so take it with a grain of salt) most questions are in the order of the passage. That is you can expect to find the answers
for first few questions in the first paragraph and so on. Once you have read the questions, you will als have an idea if a particular paragaph you are reading could have the answer to a particular question or questions.
3. Once you have read the questions, do a fast scan through the passage. If you find any answers, underline the relevant lines and indicate which
question it answers.
4. Underline any key information that may help answer the questions you have read.
5. You will get better at this as you practice more.
Reference/Practice Books:
Cambridge English: IELTS 11 General Training with Answers First Edition,2016 IELTS 11 General Training with Answers
Cambridge Vocabulary for Ielts with Answers and Audio CD
Cambridge Grammar for Ielts with Answers and Audio CD
Barron`s IELTS Practice Exams
Barron`s IELTS (2 CD Free)
Good luck!!
