Recently published on the Help My Resume blog:

Follow the lead of the CEO. Yes, it might feel outdated, but he or she is the one writing your check. If he or she is in asuit, you need to be in a suit. If he or she prefers adress shirts and slacks, plan to prefer them, too; ditto, T shirts and jeans, etc.

No one in the C-Suite wants to be anxious about taking you into a meeting with potential clients. They also don’t want to be worry that you are going to have a wardrobe malfunction in an internal situation.

Note, too: If your boss doesn’t dress down on Friday, you don’t either (if you want that promotion)

Finally, in addition to clothes being too casual, you can also have hair that’s too casual Get it out of your face. Tidy it up.