IT’S NOT THE WEEKEND YET
Far too many people believe that casual Fridays are an excuse to dress as they would on a weekend. They think that because the word casual is used T-shirts and flip-flops are an acceptable wardrobe choice. This could not be farther from the truth.
Ostensibly casual attire simply means that suits and ties do not need to be worn. It's that simple. So long as you are not wearing a suit you are not over dressing for casual Friday; now on to the more tricky bit, how to ensure that you do not under dress.
IF IT HAS A COLLAR YOU’RE GOLDEN
When it comes to wearing shirts that must meet the criteria of casual attire for the workplace it is always a good idea to ensure that the shirt you are wearing has a collar. It doesn't matter if you're wearing a polo shirt or a formal shirt, so long as it has a collar.
If you choose to wear a formal shirt your next decision will be whether or not you wish to wear a tie. Either is acceptable, and on casual attire days you can experiment with your tie selection especially if you have quirky or humorous ties that you've always wanted to wear to the workplace. Just remember, keep it tasteful and avoid any tasteless novelty or big-picture ties.
If you choose to go without a tie then feel free to unbutton the top one or two buttons of your shirt. Obviously you don't want to show too much skin, however unbuttoning your top button projects a more relaxed look that is appropriate for casual attire days. A good collar option is one with a button down collar.
The golden rule here is to keep it appropriate for the workplace. That means never wearing a T-shirt or Hawaiian shirt to work. When in doubt just wear a polo shirt and call it a day.
KEEP THE SHOES CLOSED AND YOUR TROUSERS PRESSED
As far as shoes are concerned; so long as you wear closed toe shoes to work you will be fine. Some people believe that only loafers are appropriate on casual attire days. This may have been true at one point in time; however it is no longer the case. Smart, clean trousers are also an important part of finishing your casual attire look. Denim jeans and relaxed chinos are perfectly acceptable so long as they are clean and pressed. As a rule of thumb leave any trousers with holes in them or frayed bottoms at home with the sweatpants where they belong.
RESPECT THE LATITUDE YOU ARE GIVEN
These are all of course very general rules that may vary between workplaces. Obviously, if your workplace has a specific dress code for casual attire days you would do well to follow this dress code. Remember, what your employer gives your employer can similarly very quickly take away; and your choice of wardrobe may not be the best issue for you to take a defiant stance on. Always keep in mind, whether it is on a casual Friday or a regular Monday, always: Dress to impress because a man may have brains but, you see his clothes first!