Language is one of the most common ways we exclude people. Be aware of this.
This is something that happens at tech events, especially to women. A woman is having a conversation. Someone says, "Oh, are you in marketing/sales/etc?" That's so insulting to someone who has spent just as many years building their career as a man. She is assumed to be non-technical because of her gender. Don't do this! At a technical event, not everyone will be technical, but go on the assumption that they are. A marketing person is not likely to be offended if you think they are a developer.
That said, don't assume anything about anyone! It's much easier to say "So what do you do?" It's a very easy question and the most natural opener at a professional event. Learn to ask instead of assuming.