Frankfurt is an expensive, business-oriented city, and you can save a bundle by booking one of the air-hotel packages available from major airlines. Note that hotel rates can almost double when there is a major trade fair going on. Finding a room, not to mention one at an affordable price, depends largely on the busy trade fair schedule. On average, there is one a month; the tourist office maintains a schedule online at www.frankfurt-tourismus.de. It's best to reserve well in advance, but if you need to make a last-minute booking, contact the friendly staff at the tourist office.
Most of Frankfurt's accommodations lie around the fairgrounds and the train station (the latter is designed for convenient arrival and a quick escape). The station can be considered central, although it may require a walk through the less-than-picturesque Bahnhofviertel in front of the main station, and bordered by Mainzer Landstrasse, Taunusanlage, Gallusanlage, and Münchnerstrasse. Unfortunately, this is the only side of Frankfurt that many see, leaving them with a dim view of the city. Alternatively, consider hotels in Westend, Ostend, or across the Main to get a perspective of the city that many casual visitors miss.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.