Good luck on the first one! But, "luck's got nothing to do with it!" Reality is, the seller likely doesn't know what to expect either so don't worry about what's "proper" just make it "your" meeting. Treat them respectfully and be pleasant.
Keep it simple, bring the contract with you. I would fill out the contract for time sake but I don't think it really matters. You can build rapport by filling it out with the seller so they feel engaged in the process.
Generally upon signing a PA, a licensed agent is required to also give a set of disclosure statements; sellers disclosure, lead-based paint, and a licensing disclosure. If you aren't an agent though, don't worry about it. Two "Principals" in a deal can make any deal they want. For a valid contract you just need an offer (signed by buyer) , acceptance (signed by seller) & consideration (earnest money...whatever amount you agree on).
If you have any additional information about the home, yourself or company, it is always good to have.
Is this a first meeting? Have you already negotiated a deal? If you are there to get a PA then just get the contract signed. Anything else you need you can get at a later time (in case you forget something)
Things the seller will need from you:
They may ask for an earnest money deposit - certified funds or cash commonly $1,000
Perhaps they will ask for a proof of funds letter verifying you actually have the money to buy their property; bank statement, 401k statement etc. wherever the money is coming from to fund the deal.
Anything else they would want or will need to produce you wont need on your first meeting and likely you wont need any of these things right off the bat. Each deal is different and will require different things to be verified so once you see what the deal is tell them you will get back to them in a day or two with the information you need from them.
The most important thing is for you to be confident with yourself. The other guy doesn't know your experience level so have a game plan of how you want the meeting to go and stick to it. If something comes up that you don't know how to handle, tell them you will get back to them on it. Don't give answers for the sake of giving answers. No shame in not knowing everything.
Welcome to the business!! I wish you success!!