A small reference notebook
Read with a small question
Choose a purpose
Before opening a long text, write down one question you hope it can answer. That question gives a first pass some direction. It also helps you notice when a text belongs to a different subject and should be saved for another day.
Keep context nearby
A sentence can mean something different when separated from its paragraph. When making a note, keep a reference to the surrounding section and the edition you read. A short explanation in your own words is often easier to revisit than a page of copied quotations.
Return after a pause
Leave a little time between reading and reviewing a note. Try to describe the main idea before looking at the original again. The gaps that remain are useful: they show which parts need another careful reading rather than another pile of highlights.