Have been here as an expat for awhile. Hangzhou is unique in that it is quite affluent and many girls are worldly. But many friendly girls for a guy who acts sane. Take it easy is the rule I follow.
World Trade Center Hotel sauna - Had great girls 6 months ago, but crackdown recently has toned down service. I am in contact with the woman who runs the place and it should be back to normal soon.
Foot massage, etc. Take the time to go have one, and if you are lucky enough to get a cute girl, order a shoulder and back massage. You will be taken to a different room and have time alone with the girl. No hanky panky there, but usually she will be willing to exchange mobile numbers.
Asiafind, etc. Worth a try, but time consuming and hit or miss.
QQ - Get the international software and give it a try. Join your city Darren and you will see scores, even hundreds of hot girls.
Craigslist - Useless. All pix fake.
Girls on street - Unless she makes eye contact, leave her be. If she does, chat and exchange numbers.
Find an English teacher through normal channels (HZ Expat, Craigslist, etc.) Many girls long for a foreigner but are too shy to go the direct route. Teaching English is a way to contact foreigners legitimately, and then pick and choose who they like. 50/50, but I have met a couple of very sweet and kind girls this way, and struck up an ongoing situation. Be very gentle with these girls.
Clubs - I do not have much experience with these.
Bottom line - If you are coming and going, Hangzhou is not the best place. But if you spend more than a month or so, and you are a normal guy, you should do OK.