The easiest thing to do is just casually ask the host, "So, what are you doing this weekend?" or whenever the party is. If they say they're having a party but they don't invite you, or if they say nothing about the party, you pretty much just have to accept that you're not invited.

How do you get invited to someone's house?

Hang around with her friends. Wait until you find a weekend where they're doing a project that you can help with. Tell the people that you know all about how to do the project and wait to get invited to their house to help. Study up on the topic if you don't actually know much about it.

How do you get a guy to invite you to his house?

Give him ample notice before the proposed hangout time. If you call him up a few hours before you want to hang out, he may say no due to prior plans or because his apartment is messy. Be clear about when you plan on arriving and leaving. Tell him you have a commitment and will need to leave his place by a certain time.