For the next four days, Berlin will be (another) the beating heart of the world tourism, with the famous ITB opening its gates first for professionals, and after (during the w/e) for the large public. As this year my schedule for the next week is extremely complicated, I will miss this event, but I will share shortly my last year experience.
First of all, the place - the usual destination for the big fairs in Berlin - is huge...You need more than 4 hours to see 80% of everything...And to swim across people, long lines for free gadgets and various events meant to attract the attention of potential tourists - live concerts and dance performances - last year I assisted to one from Macedonia and one from Turkey. The most populated places were the exhibitions of North African and Asian countries. Most probably, given the current turmoil from the Middle East, the Asian destinations will win more clients. The public was of all ages, but the reliable clients were, obviously, couples of 50+, especially for long, exotic and also expensive trips.
Shortly, before embarking for the ITB experience, be ready to: spend there like a working day, be fit enough for walking for hours and waiting for various gadgets - from leaflets, pens, CDs, various bags, TShorts... - and be sure you have a good budget dedicated to travels for this year, otherwise you'll resent a deep frustration to see the world opening in the front of you without being able to go out of your Berlin winter (which is better than the permanent sun in other parts of the world, sometimes).