I offer a hug to anyone who I'm not in a professional relationship with. Most people seem to like this, and if they don't, I switch to a 'bro hug' in mid-motion. Nice and simple.
I think this is a nice technique and have tried it with more or less success, also, I tried to appeal to the normality of hugging someone by just calling someone out "Stop whining and hug me please!" :)