Effective negotiation helps you to resolve a situation where what you want conflicts with what someone else wants. While some believe it is best to negotiate with the expectation of getting what they want regardless of the needs of the other party, the better approach is to get what you want while considering the needs of the other party. Negotiate to Win-Win, not to win.
When you don't expect to deal with the other party ever again, or you do not need their goodwill, then it may be appropriate to play “hardball", seeking to win a negotiation while the other party loses out. Many people go through this when they buy or sell a house, which may be one reason why negotiating a house purchase can be an unpleasant experience. However, this approach is not much good for negotiating with people with whom you have (or expect to have) an ongoing relationship, such as a vendor, service provider, employer, etc.
Playing hardball with someone with whom you have an ongoing relationship may damage that relationship and lead to reprisals later. Using tricks and manipulations during a negotiation to disadvantage the other party will certainly undermine trust. While a manipulative person may not get caught if negotiations are infrequent, this will not be the case when people work together routinely. In that case, fairness, honesty and openness are the best policies.
The negotiation itself should be a careful evaluation of your position and the other person's position, with the goal of finding a mutually acceptable compromise that gives you both as much of what you want as possible. In an ideal situation, you will find that the other person wants what you are prepared to give, and that you are prepared to give what the other person wants. For a negotiation to be "win-win", both parties should feel positive about the negotiation once it's over. This helps people keep good working relationships afterwards.