It is difficult being a SG on any site. As with any other social gathering you go to pub, club etc you strike up a conversation and see how it goes. If you are looking to get laid straight away then, well say no more. Would you start a conversation with a lady and after 10 mins ask if she wants a shag, no or if you do then watch out for those slaps. The same principle applies here, chat, get to know the SL or couple see how it progress's. Rome wasn't built in a day nor are friendships. In my opinion most people on the site are weary of SG, either from bad experiences or not interested.
For me it took over 5 months of trying to get a certain gorgeous lady to talk with me and I'm so glad I kept trying (felt like stalking and at times I was uncomfortable just saying hello for that reason). Many times I felt like throwing in the towel and becoming a monk, but you just be yourself if people don't like it then it's their loss.
One last point, I do think it's rude if you say hello to people and they do not reply, even if they just say thanks but no thanks. Curiosity goes both ways. xx