Good designs convey information that the target audience can quickly understand. But how do you know if your designs are working? How do you know that your target audience can quickly understand your solution? There is only one way I know of – ask them! Show them – walk them through the design and see if it works. If it doesn’t then make changes and ask them again – rinse and repeat until your designs do their job.
This is prototyping. Something I am very passionate about. “If a picture is worth a thousand words, a prototype is worth a 1000 meetings” (credited at @ideo). You can write a description of what your solution is supposed to do – but that won’t tell you if it actually does it. You can make some “pictures” of what it does – that can eliminate a few thousands words but still not tell you if it does it job. But a prototype can convey what the solution does. Something you can iterate on until you get it right.