assignment contract help!!!

well im in the middle of assigning a contract for my first deal. im a little confused on a few things, i have a buyer who wants to buy property in my area, i did find a few properties in my area that she is interested in. i found the property on the mls. she has ask me to gather all the properties in my area that meet her criteria, to meet her tomorrow. should i wait til she picks a property from my list then do u think i should go to the seller and negotiate a price with him or her and if agreed im suppose to lock up a contract with the seller right? what kind of contract (agreement to purchase, or purchase and sale agreement) then when a contract is locked up with seller i go back to my buyer and tell her that im going to assign the contract to her using an assignment of contract correct? what if when i show her my list of properties and she picks one but then says i would like to go see the property with you today, what do i do, do i say yes even though i don't have a contract lock up with the seller or do i say no since i dnt have a contract with seller. can anybody please help me before i make a fool of myself...please explain the steps anyone...