The minimum size of an Active Area (AA)
Ideally, it is 48 x 48 pixels. However, there are elements that needs to be smaller in relation to other elements with it—with this consideration, we could go down until 32 x 32 pixels.
The cohesion between two UI elements
In order to show cohesion and relation between two UI elements, we could use proximity—place the element near each other. However, when there are more important considerations like if space won’t permit one element to be there, we could use motion to cue that those two elements belong together.
The elements in relation to the user’s “now”.
Elements that are there only when you need it and also there when you thought you didn’t need it.
Numbers 3 and 4 fall under Relevance.
Outcomes Over Features
The outcome most teams are aiming for is a change in behaviour. The outcome you want will depend on your business or organisation: it might be selling more dog food, getting people to sign up to a monthly donation to your charity, or opting for mediation over court in their separation. Source
Shareability of Content
When deciding the number of characters an item could have, consider thinking about it being in other platforms.