Short answer: Pick a topic you care about, read a few pages daily and note ideas in your own words.
Pick a topic
Start with a topic that interests you.
Small goals
A few pages a day builds the habit.
Notes
Write one-line takeaways.
Frequently asked questions
Is it useful for exams?
It builds reading speed and general awareness.
Where can I buy cheap books?
Browse second hand books on Bookaao.