I sometimes make Tridents on my flash cards eg
The 'main' heading:
Rivers
Then make three branches from the word Rivers, which correspond to it,
So upper course, middle course, and lower course.
Then at the back, write about them in more detail.
Also for me; colour is a must. I need various colours especially ones that contrast each other, I mainly use: Pink/Purple/Blue/Green/Sometime black.
Also highlight things
Would also be good if their was an option to say copy paste a URL of an image, which can be directly added onto the flash card. Along with this, maybe a feature to insert your own image, though I prefer the URL method. It may even be a good idea to have the ability to draw mini diagrams, like in paint.
Different types of fonts, underlining things etc...
I like to include like weird borders around small pieces of texts if that makes sense,
It would be good if there was a feature to add text boxes onto them - so you can have say 3 text boxes of text within the flash card.
Would be good if you can include spider diagrams as well. So it can automatically make it for you - and maybe a more advanced feature; to link things within the spider diagram so eg:
Central theme: Rivers
Arrow pointing to: Meander
Then within the meander have another arrow to point to: Bend in the river.
For languages (speaking exams), I like to write the question on one side then answer on the other.
Sometimes what I do is write about something on one side, for example "Rivers contain: Waterfalls, gorges, meanders and Ox-box lakes"
Then at the back I'll write a rhyme to help me remember that, eg "Williams games meet oranges"