The ticket columns of the public transportation system 'Uestra', called tix. If you want to buy a ticket be sure to have exact change. (That has changed! Some give change now, but still they don't take bills!) For prices check www.uestra.de! The page is available in German only, though.
I would say. We hardly have many tourists in town. Maybe that´s an advantage for you, you will see the real Germany away from all the tourist paths.......
During Cebit time I would mind to go out in a local restaurant. They are all crowded, the prices are high and the service or food isn´t that good as usual... That´s the only fair guest trap!
We don't really have any tourist traps - because we don't really have any tourists ;-)
The only one I can think of is several Bavarian restaurants in town that make foreigners think that's what Germany is really like. Oh .. and avoid the old town during CeBIT time.... definitely no locals there!
Herrenhauser Gardens/ Rainforest: the Gardens are beautiful and you should visit them, but during the summer they charge 6 Euros. I paid once to see the gardens in full beauty and they had recently removed ALL the flowers and the fountains were not running. Take a peek in the gates to ensure its a good day to visit. As for the 'Rainforest' tourists pay some silly amount to walk around a small building with tropical plants. Instead pay 1 Euro and stroll the gardens and greenhousees.
This is almost an 'anti' tourist trap, but there's a red line painted on the ground through the city centre, which will lead the visitor to several significant points of interest.
At the tourist centre in front of the train station, on Ernst-August-Platz, you can pick up a copy of 'The Red Thread', which will point out the sites, along the pavement, across roads, into subways, etc...