I was in Erdek for about 2 months, but this was back in 99. Good place to get inexpensive custom made leather jackets. I've never worn one before but some friends convinced me to get one and it actually looked pretty good. It looked kinda like a regular suit top with the lapels and pockets but it was just made of leather. It was also a good place to get gold jewelry for cheap but this one i didnt get any of these cause i never wear jewelry. A lot of the people i went on the trip with bought all kinds, but mostly custom made cartouche necklaces with their names on it. Last one is ornamental shotguns but i dont think anyone got any, maybe 1 person the customs paperwork would probably be a pain.
I would recommend trying out the local food too. Doner Kebab is pretty good...those are like lamb roast things that you'll see on a vertical rack. And they'll cut thing slices off of it and serve it. There is also a Turkish style pizza called Lahmacun i think. Its made of pita bread that is slightly crispy and its got meat and some veggies and no sauce. I dont remember since its been soooo long but i remember it having finely ground beef or lamb. And it was so good that we ate at the same Lahmacun place almost every day.
For the fun/sex? sorry cant help you there. For staying out of trouble only thing i remember was dont disrespect Attaturk (their founding father) or anything that has his picture like posters or money. And also dont Proselytize...but if you are asking about fun/sex i doubt thats something you were planning on doing hehe. There is probably other stuff but those were the ones i remember cause at the time i believe you could go to jail for those things. Ohh and also, dont travel alone bring at least 1 friend or more from back home. Dont make a friend over there and have them be your travel buddy. Attacks on foreigners in Turkey *do* happen and it can be anything from a simple beatdown to having your ass blown off in a car bomb or getting shot at.