[rnd33]

Dressing appropriately does not mean "dressing up". It means dressing slightly above what is generally accepted as the normal dress code for the role your interviewing for, and the culture of the company. This is what makes it so hard, if it was just about putting a suit on everyone could do it.

If you're completely unsure, just call the hiring manager and ask. "What's the dress code at company X?", "How do people in role X normally dress at your company?". No one will be mad at you for making an effort and trying fit into the culture.