Leafing through booklets, handouts, worksheets and textbooks can be overwhelming which is why we love the Post-it note rule. A lot of tenses and language 'formulas' can be summarised on a simple Post-it note.
Let's take the Spanish imperfect tense as an example, divided into their conjugations:
The Imperfect = habitual actions in the past/was/were doing
Sounds like = -aba / ía endings
E.g. = Vivíamos en España (we used to live in Spain)
AR verbs ER/IR verbs
The formula fits nicely onto a Post-it note; adding the example and the translation underneath will help visualise the theory into practice.
Plus, sticking them somewhere visible such as a mirror, desk or door, means it's in your eye line and grab your attention. Once you've learnt the rule, replace it with another one!