As they said to you already, make sure that you will bring some gifts to your gf’s family from your country. This will serve a dual purpose…a. Show respect to your gf’s family and appreciation for their hospitality. b.the gifts will be a very good topic for breaking the ice…explaining to them what is what…of course if your chinese is close to non…(as was mine when i first met my now in-laws) your gf will have to do the translation. Other than that eat from what is on the table…even just a bit. If they have a pet play with it (unless it is a 6 meters python 
) Just be yourself
Eat a bit of everything that is on the table, especially everything that is offered to you. I have to remind my wife not to explicitly offer me things that I cant stand as it really doesn’t look good to refuse some of the things I really cant eat. The “Aunties” will have a big discussion about which things you didn’t eat and why.
I learn’t this the hard way when the aunties thought I didn’t like their food — they made me some extra special dishes that I would surely like. (and by extra special I mean even extremely more strange or difficult to eat dishes)
Tibetan New Year is March 5 this year.
If you refuse to eat something it could be just coz you are a foreigner and foreigners are strange and have there own customs and stuff.
You can refuse to eat the stuff that has sat out on the alter by saying you are a Christian. Especially in summer.
Don’t lie and say you like something you don’t. You will forever regret that as they will buy or make extra and make sure they ply you with it every time you visit.
Everything in Duke’s classic post is so true.
I’m looking forward to it. Father-in-law will put a beer in my hand when I walk in the door. We will ensure each other has copious betel nuts and cigarettes. I will not pick up the lobster until it is offered to me. I will immediately go for a piece of the big fish, lest the fisherman feels offended, and toast the father in law early and often.
When the guests leave and everyone takes a nap, I’ll drink all the left-over beers and watch TV.
Thank Christ-Almighty for TV. Fortunately, there’s one in every room.