You must request clarification from your family as to the degree of witnessing or authentication required.  

If witnessing, you need two persons who will sign their name and write their address and maybe passport number after they see you sign the papers.  Or it could go all the way up to you seeing a lawyer, identify yourself to him with your passport, sign papers in front of him, and he in turn will write a short statement to the fact that he verified your identity and witnessed your signature, and sign and seal it.

But you must know first exactly what do they mean by "authenticating" your signature, and required means to do so exactly as needed.

In legal terms, what you require then is called "witnessing the signature", not really "authenticating" it.  Get two friends, any sex, if over 21 better, and with them you sign the document in their presence.  Below, hand write "witnessing the signature by " and each friend will sign, and below their signature affix their full name (as shown on passport or ID), address, phone number and either passport number or ID number. No need to go to Embassy at all.

Not really required, but since I do like the added touch, you can have them affix their right thumb print to the right of their names as they do here in China with documents.

It was a pleasure helping you resolve this "crisis"  !   

Sorry Happy, but this is to be done by the notorial authority in the region she is in. The stamp that she needs must be by an official notary and is easily received but you can't just have two people sign the document unless a government official is present and can give his signature stamp. You can find any notary service on line and in English for Beijing. Or you can come to me and I'll stamp it for you with two signatures of legal assistants but, it'll cost more than having it done by the a Chinese notary.

Techezee, by no means I wish to take business away from you, but there are two levels as I said in my original posting,  One level is to have your signature witnessed by two persons, and I have done that many times at the request of my bank in investment transactions, and at the request of my lawyer in USA for legal documents to be used there.  Also, I have served as a witness of signature to a friend who needed to retire investments in UK to buy a house here.  There is a second level, more stringent, that will require a notary to certify and stamp that the person named was in fact the one signing, and that also the two witnesses are indeed who they claim, and did witness the original signature.  This, for example, is required on an open will who will be filed in Court for the record.  I have also done it that way, and have served as witness for friends when they wrote their will.

I have no idea was Ammia was required, thus I explained both ways to her.  She should either confirm or clarify which way is required, and for what purpose it will also be used.  In rare occasions  another signature and stamp from the Embassy may be required, but not normally, it will depend on what the document is needed for.

Happy, I'm no where near where she is, I was just telling her how easy it is to have it done by a notary in Beijing which there is a cheap legal notary on almost every street around SOHO