Knowing how language works will go a long way to your success in the reading comprehension section. Teach yourself how to puzzle out words you might not understand on a first, casual reading. Look in the dictionary at a list of multi-syllable words and see what syllables they have in common. Most words are logically put together. Most comprehensive dictionaries feature a table of Latin root words. Study these tables so that you can deduce the meaning of a word based on its root word influences. You do not necessarily need to memorize every single root, but in time, you will begin to see certain consistencies.
Many students taking the GED make the mistake of reading each passage completely from beginning to end. While it is important to pay attention to details in your reading, you must read strategically when taking a timed test. This means not becoming bogged down in information you do not immediately comprehend. Instead, read the questions assigned to each reading section first. This way, you can know what to look for before you actually read the passage. This is important in most sections of the test, because regardless of the subject, the GED tends to embed most of the test answers in the reading passage. Knowing how the make the best use of the time allotted will give you additional time to figure out those questions that initially stump you.
The science portion of the GED tests practical physical and chemical actions, and reactions. Read the scenarios carefully, never merely picking what seems to be the "obvious" answer. Instead, take into account what you know about how objects behave in daily activities, such as shooting a round of pool or a game of hoops with your friends. Gravity, leverage points and oxidization (rusting) are all common areas explored in the science section of the GED.
You will scratch paper to work out math problems. Solve the problems that take the least amount of time first, then go back to work the brain teasers. Fractions and ratios are often stressed in this portion of the GED. Cram for these.