Start with something inane, like about the weather or an airshow or anything that most people would know about. Don't seem too interested in them... wait, strike that, don't BE too interested in them. Just chat. If it's going to become more, it will, and you won't have to force it. Be polite, be friendly, act like you wanted nothing more than to exchange a few pleasantries over a beer. Be comfortable -- I know, if you knew how to be comfortable you would not have started the thread. Just try different stuff, and if it doesn't work, don't do that anymore. Be willing to fail. Be yourself, if she doesn't like it, then you won't enjoy being around her in the long run anyway. Relax.