Michelle, it's a reasonable question. If you'll dig around (although it might be hard to search for), we've had a couple of threads on this.
I think the consensus is that, um, it varies. Corporate fast-food places like McDonald's or Taco Bell aren't really set up for tipping, and in fact (opinions vary), staff may be forbidden to take tips and subject to discipline if they do so.
But local indie places? Chances are the person at the counter also had to take time from other duties to set up and box your takeout for you. Bottom line, most people in the restaurant business or close to it will err on the side of generosity and tip service staff, period. And I'll generally do that, certainly at the Cajun place and the Middle Eastern place you mentioned.
Same way for tipping the guy well who brings the pizza to your door ...