1. Mostly, people are more worried about what you think of them.
This is like that thing about spiders. You know, they're more afraid of you than you are of them. Which I'm not sure whether that's actually true or not or whether that's just something parents say to make you not freak out in the presence of a spider, but that doesn't matter. What I'm trying to say is - when you are lying in bed late at night worrying over how you dropped a glass or said something inappropriate or whatever else, know that everyone else is doing that too. Only really petty people sit around judging others - mostly people are just worried about how they themselves came across, and whether you liked them. So ask people questions about themselves! Listen to their replies! Be genuinely interested! They will appreciate it.
2. You might think you're awkward and weird but it's entirely possible you're superbly adorable and charming.
Everyone sees themselves differently to how other people see them, and every person you know perceives you differently to the next. So if one person tells you, 'Steph Bowe, you're too shy!' don't worry! Unless your name isn't Steph Bowe. In which case, why are they calling you Steph Bowe? But seriously - you're probably a lot more critical of yourself than other people are of you. Thinking that you are weird or something else shouldn't stop you from going out and having fun. (And often the things that you think are flaws are the things that other people find absolutely charming.)
3. No one really cares.
This isn't supposed to be depressing - it's actually very freeing. Basically, quit worrying and angsting so much about what people think of you or about how shy and awkward you are, and remember that no one really cares if you are a little shy or you stand on someone's foot or whatever. Go out and be your lovely, wonderful self and they will like you or feel indifferent towards you and it doesn't really matter because you are still fabulous and we're all self-centred and this is ultimately a good thing! If you do do something really embarrassing, know that people forget really quite quickly, if they noticed at all. It's usually only a big deal to you.
4. Smile more.
My normal, neutral-mood face makes people think I'm upset when I feel just fine. I think a lot of people are like this. If you have meanface syndrome, smile more. Not to a creepy degree. Bring a friend with you to parties who can subtly nudge you when you begin looking like a serial killer. Practice this. Go find a mirror. You have a lovely smile. Speaking of bringing a friend - get a wingman/lady. My mum is an absolute legend, so I bring her along whenever she's not busy being awesome elsewhere. Having an outgoing person with you makes it easier to go places where you don't know many people. And if it turns out to be a terrible party and nobody talks to you, you will still be able to have a fabulous time.
5. Put yourself out there.
The more you put yourself in social situations that are out of your comfort zone (parties where you know one person, etc) the better you will get at talking to people and feeling comfortable and having a good time wherever you are. There's nothing bad or different about being shy, but don't miss out on meeting different/new/exciting people because you're worried you'll awkwardly hug everybody (feel free to awkwardly hug me. I'm a big fan of the awkward hug) or no one will talk to you or you'll have nothing to say. Because, really. I am shy and introverted and awkward(ly charming) but the more I go out and talk to new people, the more comfortable I become with it (people actually sometimes don't believe me when I say I'm shy now. Which is hilarious). Recognise that you are a fabulous person and look forward to the many great parties you will attend and conversations you will have. Smile and make eye contact and listen and hold your glass upright! You extroverted legend!