Try getting good clothes. Go to a good store and let the people do their thing. (Or otherwise find some fashion advice).
I did this as an experiment a few years back. Just walked into a place, gave em some cash and said make me look less of a dork. (I usually just wore slacks and a plain tshirt, mostly dark colors, nothing worth noting other than it's lameness and banality.)
The difference was immediate. Night and day. People just noticed and responded better to me, everywhere. It was like this secret power, just putting on a Wardrobe of Charisma +5. It was bizarre.
I haven't kept it up at all, mainly due to lack of need of charisma in general. I've known that dressing up, like wearing a good suit, can be effective in social engineering situations, but I wasn't aware of how powerful just dressing "nice" versus "usable" had just walking around.
I'm sure this is all well-known to most people and you might be shaking your head at the basics of life I am so amazed by, but perhaps someone will find this an interesting anecdote.
Edit: I'd also note that I did what he suggested, too. I look back at my blog and cringe. But I got a fair amount of contacts, book deals (which I never followed through on properly), even respect from strangers on a few occasions, on account of me being active publicly. And back then people linked a lot to random blog posts (maybe they still do) and without any effort, I had a PR6 site which was sorta cool. As a bad career move, I got embarrassed about things and decided I wasn't as good as I thought I was and stopped writing and self-promoting. Traffic and PR went down accordingly.