When you go shopping, please take someone local with you. You will need to bargain a lot. If you don't do it, you will be paying three to four times more then the price. Also, while using trasportation, ask somebody how much it costs befoer you use any public Transportation. If you can find, keep a chart for the Rickshaw (a taxi with three wheels).
Kankaria Lake. THis is an overrated place and if U are running short of time, avoid this place. Same can be said of the zoo.
If U can spare an evening, U can better spend the time at Nal Sarovar, a bird watcher's paradise, 70 kms away from Ahmedabad.
like everywhere,most of the traps come from the taxis,or the 3-wheels-cabs;if you ask to go to such a place,if the driver does not get a commission,he will tell you that it has closed,and he will bring you to a disgusting half of a quarter of one-star-hotel,you won't even dare to get inside.