Most Helpful Girl
You will need to introduce yourself to a few people, maybe stand in groups and listen to what they are talking about, join in if you can. It might be a good idea to meet more people before going to house parties so that you have a few more people that you can hang out with when you go to parties. If you stand out people are more likely to approach you so maybe wear a T-shirt with a funny slogan or something that would catch peoples attention. The first times will be more difficult but once you get to know more people to interact with you will start to relax and feel more comfortable and just enjoy yourself. Do you drink? Would you participate in drinking games?
Don't be discouraged, rejection is part of life, its not easy but if you don't just jump in there and give it a try you may end up living with too many regrets. Not all ladies care about looks, attraction is more important in my opinion. Be yourself and make them feel comfortable. Don't over think your appearance, this will make you lose confidence and confidence is attractive. You can talk about what she's drinking, who she knows at the party, maybe make a joke or compliment her on her eyes or smile. You could ask her who she came with. Just try enjoy it, don't have too many expectations and relax a little bit.