[Alpha Hunter Zero]

Personally I've never used this on a girl I haven't already established some comfort with over at least a few days. That way it doesn't seem weird some random guy is trying to hug her. Also what I do is instead of asking for her permission to hug her, I walk up to her and when there's about a foot or two of distance between us I slowly outstretch my arms and hug her. Simple as that. Normally there will be no resistance if there was some comfort built beforehand but if there is so what. It's not an exact strategy depending on the scenario, like gmac stated, but if you can the hug good for you.