The method-of-loci technique, which relies on spatial memory, is remarkably simple to explain, but does require some mental effort to set up. What you do is think of a place that you know really well, like a house you lived in as a child or your route to work. Then you place all the things you want to remember around the house as you mentally move around it. Each stop on the journey should have one object relating to a memory. The more bizarre and surreal or vivid you can make these images, the better they will be remembered...
... Here's an example of how one person encoded a memory to give you the flavour:
"...one participant in the main study had generated a memory of an important conversation over coffee in New York with her best friend. She associated the memory with the front of her childhood home (one of her selected loci) by imagining the fascia of the house transformed into an outlet of a popular U.S. coffee chain with her friend standing outside smiling and dressed as a barista."
Everyone rehearsed 15 of these self-affirming memories and placed them around their memory palaces. They then practised going around their individual mental routes until they could easily retrieve the memories and the associated feelings in high levels of detail.