What designers shouldn’t do?
Each designer makes mistakes during his work and it’s absolutely normal, all of us are humans, but there is a list of that thing, designers must not to do at all, if they want to reach the success in field of their creation.
The first and the main rule for everyone is that it’s forbidden to steal the ideas from other creators. No one has the same heads, so no one can have the same ideas and to do something creative it’s necessary to make something, not looking like others have, only in this case the design would be awesome.
Never save creations in only one file version, because clients need to have a possibility to open files from different programs and they won’t want to have problems with that because you made only one version.
It’s difficult to believe in, but some designers try to do their creations, using Microsoft Word. It’s laughable and any client would want to work with such creator, because of his low qualification.