Tara at Graphic Design Blog lists seven mistakes beginning designers make. It’s a pretty good list — I see the first item a lot.
- Producing two or more design concepts that are very similar
- Adding things in rather than taking them away
- Concentrating on features rather than benefits
- Not targeting the right audience or having enough gravitas
- Not presenting the finished design in the best way possible.
- Not sketching first
- Underselling your design work
Read more at Graphic Design Blog.