I started with reading books on basic etiquette and manners as a baseline. I also asked folks who I trusted (my sister, fellow geeky/awkward folks) for genuine feedback which helped identify the issues no book can help - for years I would actually look at someones mouth instead of their eyes and didn't realize this until a girlfriend told me. Like most skills, it's a slow walk up a mountain - just keep taking a step every day, have conversations with strangers, pick up an on topic blog or book as it's useful.