It would do you well to do a little homework before you go. While others have made some very good suggestions (comfortable shoes are a must) I'd like to suggest another aspect. If you plan to explore the city beyond McCormick Place, lots to see and do, there are areas you need to be mindful of. Search for the most current crime area reports on the internet, the neighborhoods can change every couple of years. While many dangerous areas have been gentrified (Logan Square, Lake & Halsted, etc) and many are ok during the day (Chinatown, Lakefront) it's probably best to not be there after dark when the crowds leave. As a general rule if there's crowds there's less chance of trouble, although crowds also draw pickpockets so safeguard your valuables. I lived/worked/frequented many of these areas while living in Chicago for 20 years. The face of many neighborhoods may have changed in the 10 years I've been gone but the potential for trouble almost anywhere has not. If you know what a bad inner city neighborhood looks like then that should be your guide. Take a map with you that's been highlighted with potential trouble spots. McCormick Place should be safe enough, it's quite the exposition if you've never been to one. Do get some of the food at the restaurants away from the show if you get the chance. The buses, subways, and trains can get you around fairly easy if you get the free maps that are readily available. Enjoy the trip.