Tony Attwood's book "The Complete Guide To Asperger's Syndrome" has been the most helpful book about Asperger's that I have read. It is current (2007) and comprehensive in scope. In the chapter on Language, he gives tips for conversing well with an aspie.
1. Avoid figures of speech.
2. Have a brief pause between your statements if discussing emotional issues or talk slowly about such things.
3. Be very clear without relying on subtlety.
4. Allow the aspie time to think of a response without rushing them to answer.
5. Do not feel uncomfortable if there is lack of eye contact.
6. Make facial expressions clear and consistent with the topic.
7. Avoid sarcasm and teasing.
8. The aspie may need assurance that you understand what they are saying.
9. Understand that the aspie may not know how to respond to praise or compliments.
10. Do not be offended by the aspie's blunt honesty.
In "Asperger Syndrome and Long-Term Relationships" (the best book I've read on aspie relationships) Ashley Stanford lists some ways to effectively use "Aspie-speak":
1. Don't generalize.
2. Be direct, honest, and clear.
3. Go straight to the main point--eliminate meaningless words.
4. Don't go off on a tangent.
5. Don't assume anything!
She says "a few generalizations may send even a simple conversation into that netherworld of incomprehensibility."