Hey guys I'm new here but have read up on PUA for while. My friend often has house parties and there are often girls there who are about a year younger due to alot of them coming through his younger brother.

My question is how would you deal with this setup? I speak to some of them on Facebook and such often but it's always been my problem that I find it hard to speak to them in person.

What kind of approach would be suited to this? How do I avoid being classed as just a friend?

Any kind of advice would be a great help

Well, your problem seems to be very basic and if you read through PUA you should already know the key. Try and be funny, tease them, make them laugh and feel great with you. Lose your shyness! There are many things you could do at a party. Try and drink a little (not too much) and you will get some (false) confidence, but this is just an extreme measure.

By the way, why is it so bad that they're one year younger? I would feel more confident with such girls!

Girls date up in age, so you should be wishing more younger girls are at your parties...
Like Mike said if you've been reading up you should get most of it. Approach/open, kino, #close or better. It's a little generic to tell you much more.
If you have a hard time opening try doin a trick or magic type stuff. I can breakdance, do card tricks, simple scams, clap with one hand ect. Find anything like that that you can do and theres your opener, speak to them like your would on FB. To not get friended don't do things friends do, "get me a drink" friends would get her one, but you gotta make her work for it, "I wanna be a architect" friends say "cool, I hear thats a really great feild", but you say something like "why not skip that and be a stripper?" (credit Gambler for that one). Assume rapport and act like what you wanna be.