Use the following techniques:

• Take notes as you go along - referencing them to page/paragraph/line number, so you can easily re-check any material.
• Summarise material in expanded note form. This will help to clarify your thoughts, and will provide you with a permanent record for revision.
• Include direct quotations where relevant but do not let these become a substitute for your own ideas. 
• Always work actively -how you interpret the material is central to academic study.

Tip: Highlighting and underlining of the primary text should be used with great care. Some argue that by leaving a trace on the page you can quickly tune into your initial thoughts. This may be true, but it can stop you viewing the material in a new light.