This is probably one of the simplest tips. Yet I’ve seen ignored over and over again.
When casting commercials, cast the best actor period. No exceptions.
Don’t get caught up on things like body type, hair color, eye color, race or even sex (sometimes.) There have been many, many productions struggling to make it through the day because someone thought an actor was attractive or they think someone “looks right” so they cast him/her. Then the actor struggles on set to nail the performance. The actor performs retake, after retake, after retake until everyone lowers there expectations or the director decides he can just creatively cut around the bad performance.
The flip side of this is being creative and rewriting a character from a white woman to a black man if the best actor available is a black man.
I once had a man read for a woman’s role in comedy spot. He was roll-on-the-floor funny but we did not have the client’s approval to make the change. He would have possibly been funnier than the female actor we cast even though she was great.
Acting is a creative art that very few people excel at. A great actor can make you believe the part even if they don’t fit a preconceived notion of who they should look like.