Point 1
If you find your self in an argument with a client or possible client, consider if it positively matters if you are good. Most of the time you will have nothing to gain, however, a lot to loose. If you mediate that you need to win then just request yourself why you need to win and how much you positively have to gain, it may change your actions.
Point 2
By developing a mental state of always being helpful you will find that people are always contented to talk to you and will sense compelled to return favors and refer more business to you.