In most things, understanding trumps memorization. There's little doubt that tidbits of information can easily be memorized, but it's only when you "get" it, on a personal level, that you truly know the subject. Unfortunately, some things must be memorized. There's no way around it. Multiplication tables, the order of operations in math and your wife's birthday are important to simply memorize. Sometimes you may want -- or need -- to commit a long passage to memory. While a paragraph of words may appear daunting to remember, you use many of the same skills as when you remember simple facts.
Decide to commit the passage to memory. Psychologists teach that actively making a decision to perform or attain a goal triggers the brain to make it happen, optimizing your chances. Think about your intention to remember each time you study the passage.
Read over the passage, from beginning to end, ignoring anything but what the passage means. While understanding it actually isn't required to memorize it, knowing the meaning can only help your recall.
Write the passage out on another sheet of paper. Break it up into chunks that make sense to you. A poem, for example, may contain lines grouped together for the rhythm they invoke. You may find it easier to understand and recall the text if you form new groups, organized logically to you.
Recite the passage again, reading out loud from beginning to end. This time, listen to the flow of the words. Just as it is easier to memorize a song or cadence, if you focus on the sound of the words and the rhythm of the lines, it makes memorization easier. Words evoke descriptive sounds: harsh, short syllables may sound like a car's honking in a traffic jam, for example, while "s" sounds may remind you of waves of the sea. The music of the language aids memory.
Take frequent breaks, resting between each reading and after every memorization session. Your brain processes and stores data best in short, frequent sessions.
Read over the material again, picturing the words in your mind. In some cases you may need to picture your interpretation instead. For instance, the words "Four score and seven years ago our fathers brought forth on this continent a new nation" may call to mind the numbers "47" and thoughts of you father and maybe your uncles, stepping onto another continent on a map and sticking a flag in the ground.
Make an audio tape of the passage, using a tape recorder, cell phone or computer, then listen to it after taking a break. Alternatively, obtain a copy of the passage as delivered by another person if the passage is a published and recorded source. The more senses that you involve, the more your brain attends to the information, so picturing the words and listening to them in various manners reinforces your memory.
Copy the passage again on a fresh sheet of paper. Break the text into sections, keeping the grouping that makes sense to you (in contrast to the original spacing). In the Gettysburg Address, for example, you may find it helpful to omit the commas in the first paragraph and divide the second paragraph into two sections. This technique alters the rhythm of the words and makes it easier to picture and remember. In addition, repetitively writing the passage helps reinforce the words in your mind.
Vary the times when you work on memorizing the passage. Some research suggests that everyone has a unique time period during which they remember (and perform on tests) better. By writing and reciting the passage at various times of the day, you increase the odds of finding your peak period.
Sleep immediately after a memorization session. During sleep, your brain processes information and images gathered through the day, assigning meaning and storing in memory. Similar to a computer, during periods of power usage (being awake) processing time slows down due to the volume of information. When you are asleep your brain can concentrate on the task.
Start memorizing the first section of the passage. Work with small "chunks" of the passage. Psychologists teach that groupings of 3 or 4 words are ideal for memorization, a process called "chunking." However, after practicing the other techniques you may find a larger chunk comfortable. Use your last written copy of the passage, or rewrite the passage concentrating on writing it in chunks.
Say the first chunk of the passage several times before turning to an unrelated activity. Come back and try to recall the chunk, quickly glancing at your copy to verify. Repeat until you are able to correctly recall the chunk.
Add another chunk, reciting first the first chunk then adding the next. Say it several times before taking a break. Later, recite the memorized portion of the passage as you did with the first chunk. Proceed once you are successful.
Repeat the memorization rehearsal until you have finished with the passage. Write the passage out occasionally or listen to the audio file. Remember to take breaks, especially sleeping, and jump back and forth between techniques as desired. Repitition is the basis for committing anything to memory. Repeat the steps enough times and it will move from short term memory to long term storage, which is your goal.