I was walking home from the shop that I usually visit, just down the street from my house, and on my way home a guy I knew worked at the same shop stopped me, walked up to me, and started talking about having a drink some time. I've never spoken with this guy, I know him from the shop but I don't really know him, we've never spoken; he said he took notice of all the booze I bought at the shop and the state I'm usually in when I buy it. He invited me to drink with him. He pointed out the block of houses that I live on and said 'You live up there, don't you?" as if he knew me. He asked for my bloody phone number! He's around my age and he seemed sincere in his offer to hang out with me, but I don't think I can really trust someone who just walks up to me and asks to be my friend. I don't have any friends, and I've never had someone walk up to me and ask me to drink with them. I don't know how to react. Any advice for this?