Do things even if they make you uncomfortable. You have to pretend to be interested and ask questions about their interests. Most people are egocentric so you have to pet their ego and you will be the most interesting person in their lives. You have to try to discover what is interesting about things that you find boring. It will lead to more interesting things.
Trust me, I get invited everywhere and people are really excited to have me around. I just ask them questions about their lives and try to learn everything about them that I can. After a while, you start to understand and find the same things interesting. You just haven't had the same experiences to make it interesting, and the only way to do that is by going out with them.
You can also host parties and invite people. Parties are simple. Just decorate the inside with red and yellow Christmas lights. The only light that should be turned all the way up is the kitchen where all the drinks are being served. Get someone with good tastes in music to setup an iPod in DJ mode. Provide a variety of alcohol and snacks. Jello-shooters, shots, and girly drinks are best. Also, get a keg with some cheap brand. Ask people to BYOB or snacks. Have decks of cards, poker chips, and some coffee table puzzles. Setup a few different rooms so people can make a few different social groups. Go around and have short conversations with every group and tell people that they are awesome. NEVER worry about if the party is good or bad because that will ruin it. Let it get a little out of control and wait for the police to come tell you to turn it down.
Check the local laws on noise complaints. Some places have a fine, some places will just tell you to turn it down. As long as there aren't any under-aged drinkers, and no one drives drunk, then the cops can't do much. It's okay to piss your neighbors off every once in a while. Try to arrange designated drivers so that everyone can drink and have fun.
Make sure you provide a safe place for people to crash so they don't drive. Be prepared to clean up vomit and have a few things get destroyed. $150 is enough to throw a pretty good party. If you don't have a place, find someone who has parties to tell them you have $150 and want to throw a party. Costco has everything that you need.
If you want to be super cool, get an Afro wig, wild glasses (just the frames), and bright clothing. Just look up LMFAO.
Honestly, most people are socially awkward so you need to provide an atmosphere where they are comfortable enough to make an idiot of themselves. If you are the biggest idiot there, then everyone else can take comfort in knowing that is the bar that has been set. Use common sense and don't be totally stupid. You can always just find a few party people and they will set the bar for you.
If it's uncomfortable, you can throw a kick-back. It's like a party but smaller and quieter.
