The quickest and easiest way to go to Yalova from Istanbul is to take a fast ferry  from one of Istanbul’s many jetties. The major jetties with a connection to Yalova are located in Yenikapı (south of Sultanahmet), Kabataş (near Taksim) and Bostancı (Asian side). The voyage doesn’t take more than one hour.
As of August 2008, ferry fares on Yenikapı-Yalova line are 75 TL for cars, 12 TL per each pessenger inside a car, substantially more (like 16 TL) for pessengers without a vehicle.
There are also fast ferries from Pendik, a suburb of Istanbul in Asian Side.
There is a cheaper ferry line between Eskihisar just east of Istanbul and Topçular, about 30 km to east from Yalova. These ferries take about 45 minutes to cross the Gulf of Izmit and cost 45 TL for cars, free for pessengers within the car. Pessengers without a vehicle pay 2.80 TL/person. In Topçular, it’s possible to find minibuses heading for Yalova running on the highway lying just next to the harbour.
Visit the hot springs. There are many services offered.
There are some tea gardens by the shore where you can also eat balık ekmek (a fish sandwiched inside half a bread).
The telephone code of Yalova is 226 (+90 226 when calling from out of Turkey). It used to be 216 prior to late 1990s, so old guidebooks may say so, which is not useful any more.