Being socially awkward is one of those things that serves pretty much no purpose. I know, because I used to be extremely socially awkward, probably until I was 20. (Some might say a little even now, but I don't think so). If you are reading this, then you probably think you have some social issues. The good news is, I fixed the vast majority (if not all) of my weirdo issues, and you should be able to fix yours. Here are some tips I have picked up along the way of becoming a socially normal human being.
Body language is crucial
Perhaps what makes people appear the most socially awkward is awkward body language. For example, failure to make eye contact while talking to someone is a classic mistake (I suffered from it as well) that will make you appear VERY awkward. When you are talking to someone, look at them! When it comes to other forms of body language, it's important to have good posture when communicating and try not to fidget in weird ways. Being an animated speaker is fine (and a good thing in many situations). Having a bunch of nervous ticks or other such body language issues are going to make it difficult not to appear socially awkward.
Dressing in an unusual manner also contributes to social awkwardness. I know, I wore yellow sweat pants in the 5th grade, if not 6th grade also. It did NOT help my cause. Put some effort into, at the very least, "blending in" with your dress and grooming. A lot of the time, social awkwardness is a function of the first impression you give people. Fix the easiest thing to fix, which is dressing normally.
One very difficult thing for me to do was to express interest in what other people were saying if it didn't interest me. This is a hallmark sign of "social awkwardness". Take the time and effort to listen to other people and at least pretend to be somewhat interested in what they have to say. Dozing off when people speak, making fun of what they have to say, or randomly cutting them off is not only rude, but also weird.
Avoid going off tangent
Sometimes, people appear socially awkward because they cannot stay on topic during a conversation. Try to avoid going off on random tangents when speaking. Stick to the point. If you have to talk a little more slowly to think about what you have to say, do that. It's much better than if someone asks you what kind of beer you like and you end up talking about World of Warcraft.
Be attune to the reactions of others
One problem I had that made me very socially awkward was that I was not attune to the reaction of other people to what I was saying or doing. Be more aware of how people react to what you are doing. This kind of feedback is key in improving your social skills. There is a fine line between being really insecure and always seeking validation versus not caring what people think, but the line is NOT at "not caring what people think". Once you pay more attention to how other people react to you, you can adjust your behavior to better reflect accepted norms.
A common strategy that men (myself included) use or used to improve their social skills is to imitate those who have good social skills. This works to an extent, but be careful not to overdo it and to put others' behavior in the proper context. For example, if one guy who gets a lot of girls talks a certain way about his exploits with women, it wouldn't make any sense for you, if you do not have any experience with women, to start talking about those topics and/or using slang that isn't really pertinent to you. E.g. if a guy describes something as "like some girl sucking your cock", don't use that expression if you've never had a blow job! Imitate where it makes sense to, and where it is congruent
with who you are or at least not completely disjointed.
Have more confidence in who you are and what you have to say. Don't completely shy away from conversation in an effort to avoid appearing awkward. Granted, sometimes you will make a fool out of yourself; however, if you say something with confidence, generally the result is not that bad, and it's great practice.
Humor should come naturally
Know your audience when making jokes, especially if they are complex, very corny, or weird. "Try too hard" type humor is especially bad and very common amongst the socially awkward. Let humorous things come out naturally, don't try to force something funny out of your mouth. On the flip side, if you do ever embarrass yourself, don't be afraid to use some self deprecating humor to show that you can take it and it isn't a big deal. Panicking when you do something stupid or trying to deny it when it's obvious is usually less effective than just owning up to it in a humorous manner.
There is a lot to getting better socially, but these tips should get you started. Start practicing, by interacting with people. The more people you interact with, the better you will become at ridding yourself of any social anxiety issues you may have.