I'm reading Ramit Sethi's I Will Teach You To Be Rich, and one of the tips from the first chapter is to apply for more credit card debt. He warns it's only for people like me who carry no credit card debt and pay in full each month. I don't really go shopping much with my credit card, but the goal here seems to be to improve creditworthiness, specifically credit utilization rate.
I've heard other places say that large available credit can actually hurt, because lenders will assume you run out and charge it all up the moment they approve you.
So, which camp is right? Is there a happy medium, and if so, how would I know where it is?