This is a great point. One of the best things you can do to quickly build a friendship is ask for a small favor. Borrowing a book or asking for advice are good

This is a great point. One of the best things you can do to quickly build a friendship is ask for a small favor. Borrowing a book or asking for advice are good examples. I think this only works when the cost to the favor-giver is small and the value for the favor-receiver is large. I love it when I can save someone 4 hours with a few minutes of effort. It feels great and triggers "warm fuzzies." That's why posting on sites like Stack Overflow or Quora is so addictive. But if someone asks me to spend two hours on something that would take them the same amount of time, it feels more like an obligation.