1.No Down Payment
You should receive half of the agreed upon price up front. This is a fair way to do business with all of your clients.
You should never start a job until you and your client have both signed a contract on what is expected of you. Wether your job is to design a brochure or design a simple flyer, be sure to get it in writing.
3. Borrowing Ideas from other designs
Your future as a graphic designer depends on your reputation. Under no circumstance should you “borrow” another persons ideas because you like them. This can lead to legal problems. Be safe, be original.
4.Not staying Relevant
You must always keep up with the latest trends, software, etc. Always make sure that your software is up-to-date.
Not staying in touch with your client is the number one mistake most graphic designers make when first starting out. Your client should be able to reach at all times; this means by phone, e-mail…whatever.