Recall how you find a name in a telephone book? You don't read any more than necessary to find the name you seek. Notice that you go directly down a column of news. Maybe you use your finger to guide your eyes. This type of reading is usually called scanning. Skimming uses the same type of skill mechanically but a different skill mentally. In scanning, you know what you are looking for. In skimming you don't.
Since you don't know exactly what you are looking for while skimming, prepare yourself by reading the title, source, author, and picture: then you question yourself, -- who, what, when, where is this likely to be mainly about? With a questioning mind you direct your eyes down the column of print, or in a zig-zag, if the lines are quite long. Look for exact names of people, places, things, ideas, numbers, and words like therefore, whenever, until, because, and instead, to clue you to how and why.
When you first start to learn to skim you may see only the words in bold type, italics, digits, or capitalized words. Soon you will note new or unusual vocabulary. As you become an efficient skimmer your span of perception will develop and your ability to make closure will increase.
Skimming is a step you should always take before you read any article of factual or practical narrative. You will soon be able to detect most important facts, strange vocabulary, and words that are clues to important relationships.
It's a good practice to skim everything in mass media after reading the title and first paragraph. You may get all the information you want. This keeps your skimming skills from deteriorating, or will give you the practice you need to develop necessary skills.
Skim everything you intend to read before you make a final decision to read, discard, or study the material.
Skim all highlighting and develop a read-skim pattern to use for rapid review. And don't overlook this! Reviewing frequently and rapidly is the best way to memorize (or simply remember information) from notes and long text assignments.