A friend of mine let me borrow some CDs by a dating guru named David DeAngelo a few years ago. I listened to them out of curiosity, and the advice he gave seemed pretty sound. This was before I knew about Asperger's and I never tried it myself, but it worked for my friend. What he said to do (and this is what my friend does/did) was after talking with her for a few minutes, ask if she has email. Don't ask for her address, but just ask if she has it. After all, who doesn't have email and she probably won't want to sound like a Luddite (even if she doesn't know what it is) so she'll say yes. Pass her a piece of paper (David recommended carrying some business cards or something with you) and tell her to write it down. While she's writing it, tell her to write down her phone number as well. Obviously you'll have to tweak it a little depending on the situation, but I was amazed at how many dates my friend got by doing that.