Most people don't want to be memory athletes, but they would like to remember things more easily and reliably. These techniques can accomplish that. Besides, they're fun.
Ancient Greek orators were noted for their ability to give hours-long speeches from memory. How did they pull off such astonishing feats? Since images are much easier to remember than words, they invented a visual imaging technique through which thoughts were mentally captured as images in the mind’s eye, and they recalled what was to be said by recalling the images.
One common imaging technique is known as a "method of location" (MoL). This technique is also called "Memory Palace." Mental images are attached to certain locations in a three-dimensional space imagined in the mind’s eye. The idea is to use objects in a familiar area as anchor points or pegs for hanging the mental images of what you are trying to remember. Surveys of competitive memory “athletes” reveal that 9 out of 10 use some kind of imagined location device. 
Use a memory palace
Here is a simple example: Consider the living room of your apartment or house. You are very familiar with each object and its location. You use these as mental pegs, which is easy to do, because you already know what they are. You can just mentally walk about the room and see each familiar object. In turn, one at a time, attach a mental image of what you are trying to remember on the object peg in the room. For example, suppose you identify the front door as a starting point. The first object encountered might be a recliner chair, then a lamp, then a sofa, then a coffee table, then the TV set, and so on. Now suppose you want to remember a day's to-do list. You might remember the trip to the post office by imagining the mailman at your door; the doctor's appointment by seeing a stethoscope lying on the recliner; the grocery store by seeing the lamp making a stalk of celery sprout; the bookstore trip by seeing books stacked on your sofa; the kids' soccer practice by seeing them kick the ball into the sofa; the evening PTA meeting by seeing a TV film crew filming you there; and so on.
You can use other locations or maps, such as your body, specific places in your car, or highly familiar routes in your backyard or at work. To recall these stored items, simply retrace your steps. Like fishing lines, each memory is hooked to a location and you just reel them in.
These techniques work, even for older people with no formal memory training. A recent survey that tested the usefulness of image location in older people found it effective in improving their memory capability. In a recent TED talk, Kasper Bormans described using a virtual reality replica of their home to help patients with Alzheimer’s disease “store” the memory of their loved one’s faces using the MoL. Although generally used to remember objects, numbers or names, the MoL has also been used in people with depression to successfully store bits and pieces of happy autobiographical memories that they can easily retrieve in times of stress.
Modernizing the Mnemonic
In 2012, a team of Canadian researchers gave the ancient MoL mnemonic a 21st-century facelift.  The team constructed several detailed virtual-reality environments to serve as loci, rather than asking MoL learners to generate their own. Researchers allowed 142 undergraduate volunteers only five minutes to familiarize themselves with the virtual environment before giving two-thirds of them instructions in using the MoL to memorize 110 unrelated words. A third were told to pick a familiar environment; a third were allowed to use the virtual environment they just navigated; and third didn’t receive any specific instructions on memory techniques.
Both MoL groups outperformed the controls. They were 10 to 16 percent more accurate in their recall, and students who used the virtual environment performed just as well as those told to generate their own landmarks, even though in both groups the students admitted they weren't diligent in using MoL. (It does take practice.)
The main point is that people can improve their memory ability by learning to use MoL. Although with age the brain gradually loses the flexibility to change in response to training, many studies show that MoL successfully slows memory decline in the normal aging population. Why this happens had been a mystery—until recently.
Thickening of the Brain
Any time the brain learns something, at any age, physical and chemical changes occur. In 2010 a Norwegian team set out to look for the most obvious signs of MoL-induced structural changes in the brain.
Expert instructors led 23 volunteers with an average age of 61 through an intensive eight-week training program. These volunteers managed to use MoL to remember three lists of 30 words in sequential order in no more than 10 minutes, a remarkable feat of memory. Meanwhile, members of a control group similar in age, sex and education were instructed to live as usual for the eight weeks.
MRI brain maps identified a surprisingly large morphological change in the cerebral cortex of the MoL-trained volunteers. The amount of improvement in memory performance correlated with the cortical thickening. A later study by the research team showed that MoL training increased the integrity of elderly participants’ white matter, compared to controls.
Rewiring the Brain
Two groups of researchers decided to determine whether MoL training alters brain activity patterns. Scientists in Sweden recruited volunteers in their twenties and sixties and tracked changes in their brain activity through PET scans as they adopted MoL to remember a list of random words. All of the younger volunteers—but only half of the older participants—remembered roughly four more words than they had in their initial test.
Scans of the older subjects who did't improve revealed a complete lack of activation of MoL-associated brain regions during testing. Follow-up interviews revealed that many of these participants found it difficult to associate the loci with the words under the experiment’s tight time constraints, became frustrated, and gave up. So while it's a promising technique for many, MoL is difficult, particularly for the older adults less able to generate and rely on a mental map of distinctive landmarks.
But I know from experience that practicing MoL improves one's imagination, and in turn, the ability to get more benefit from MoL. Besides, it's a more fun way to memorize.
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 Dalgleish, Tim, et al. (2014). Method-of-Loci as a mnemonic device to facilitate access to self-affirming personal memories for Individuals with depression. Clinical Psychological Science, 1 (2): 156-162
 Legge E. L. et al. (2012) Building a memory palace in minutes: equivalent memory performance using virtual versus conventional environments with the Method of Loci .Acta Psychol (Amst). 141(3):380-90
 Engvig A et al. (2010) Effects of memory training on cortical thickness in the elderly. NeuroImage. 52: 1667–1676.
 Nyberg L et al. (2003).Neural correlates of training-related memory improvement in adulthood and aging. PNAS 100 (23), 13728-33 PMID: 14597711