Once you have mastered simple memory systems such as the number/shape system, you can use mnemonic enhancers to expand the range of the systems.
As an example, you might use the convention that encasing a mnemonic image in ice adds ten to a simple number/shape image: i.e. if you have previously linked the number 2 to the word 'wine' by using an image of a drunken swan guzzling a bottle of wine, then you can change it to link wine to 12 by imagining the swan frozen in ice.
First Stage Expansion
Tony Buzan, in his book 'Use Your Memory', suggests the following scheme. Modify it to reflect the way that your mind works so that the images created are as vivid as possible:
Mnemonic Enhancers applied to: Simple Peg System e.g. Major System Normal Range 0 - 9 00 - 99 Imagine image: 1. Frozen in ice: 10-19 100 - 199 2. Covered in thick oil 20-29 200 - 299 3. In flames 30-39 300 - 399 4. Pulsating Violently 40-49 400 - 499 5. Made of Velvet 50-59 500 - 599 6. Completely transparent 60-69 600 - 699 7. Smelling good 70-79 700 - 799 8. In a busy road 80-89 800 - 899 9. Floating on a cloud 90-99 900 - 999
As another example, you could link 'compact disk' to the number 38 by imagining an egg timer (8) with its middle going through the centre of a CD, engulfed in flames (30-39). Perhaps you could strengthen the image by imagining the play of the light of the flames off the grooves of the CD.
This list of images can be remembered in correct order by using a simple peg system.
Expanding this approach again
Once you understand this technique, you can expand it again and again. For example you could take it to the next level by associating the images produced with a strong and vivid colour, for example:
Mnemonic Enhancers applied to: Simple Peg System e.g. Major System Initial Range 0 - 9 00 - 99 First Level Expanded Range 00-99 000 - 999 Imagine image coloured: 1. Red 100-199 1000 - 1999 2. Orange 200-299 2000 - 2999 3. Yellow 300-399 3000 - 3999 etc.
The expansion here might be red - 1, orange - 2, yellow - 3, green - 4, blue - 5, indigo - 6, violet - 7, white - 8, grey - 9, and black - 0. If you prefer to use colours in a different way, then do so!
Keep on expanding the method
You might to decide to expand this system to additional level by associating sounds to the images (e.g. a soprano singing, wind chimes, etc.); by associating smells; linking friends to images; etc.
So by using these techniques to expand mnemonics, you can significantly enhance the power of simple systems and the volumes of information that can be held.
At a particular complexity of image you may find that mnemonic enhancers become too complex or unwieldy - maybe after using three or four enhancers together you find that the system breaks down. This will be individual to you, and is for you to decide. This is perhaps the stage to start investigating some of the more powerful memory systems.