Before playing a sport or doing other physical activity, it is important to warm up and prepare your body for the upcoming task. It is the same way with reading. You need to warm up and prepare your mind for reading so that you can perform your best, get the most out of it, and increase your comprehension.
Before reading the text, ask yourself what you already know about its topic. Try to recall as much information as you can. Think of related ideas you've learned in the past. Make brief notes about your thoughts, or discuss what you remember with others.
One of the most important tools of pre-reading is to preview the selection and look for unfamiliar words. Write down those words, decode them, and look up their definition. If you do this, your reading will be smoother, and you will increase your comprehension by leaps and bounds!
What you bring to the printed page will affect how you understand what you read and may be what is most important in understanding what you read. A little preparation goes a long way.