The above video pretty much says it all but I would like to give you some specific examples of what it means to dress to suggest the character at a commercial audition.
This photo is an actual audition notice from my commercial agent. In addition to all the details necessary for the audition, pay rate and usage of the spot, you will see Role Name, Role Description and Wardrobe. These 3 things will inform you on what to wear.
In this case it’s OFFICE ATTIRE. This could be a dress, pants, skirt & blouse with a blazer or sweater for the women and slacks, button up shirt and tie for the men.
For UPSCALE OFFICE ATTIRE which could depict an executive, boss or manager, a nice business suit would be in order.
For NICE CASUAL I would wear the outfit I'm wearing in the video which includes gray pants and black boots. Men could wear nice slacks with a button up shirt (tie optional).
For CASUAL like a neighbor, a shopper or friend you could wear jeans with a nice shirt, T-shirt, or button up shirt for the men with no tie. I see a lot of guys with open plaid shirts in this category.
For UPSCALE CASUAL I have worn a nice black jumpsuit with a colorful scarf or body chain. Men could wear nice slacks with a jacket, shirt, no tie.
There are many more wardrobe categories and the region where the commercial will air can play a part in your choices but this should give you an idea of how and what to pick from your wardrobe. Ladies make sure your hair style matches the feel of the character, go light on jewelry in all cases, and apply your make-up accordingly. For all actors choose colors that look good on you and make sure you look neat and clean (unless otherwise stated).
If you were in a commercial as yourself what would you be wearing?