Most negotiators under-prepare. One area that is rarely even considered in a negotiation is how you will use your voice. Your voice is constantly giving a message to the other party. Without any conscious effort on your part, the message you give will generally be an accurate reflection of your feelings at the time. Sharing these feelings with the other party may or may not be to your advantage so it is too risky to let this happen by accident.

Your voice contributes up to 38% of your message (75% if they can't see you). In a negotiation, your voice is contributing to how credible and confident you appear in their eyes. These two aspects are likely to significantly impact on your chances of getting the best deal, so they deserve some attention. You can do this before and during the negotiation.

Before

Think through the difficult moments you are likely to encounter. Think about a worst case scenario (say they catch you by surprise with a personal attack). How might you react? Do slow deep breathing to settle yourself as you walk into the negotiation and be prepared to repeat this as a 'settling' exercise if you need.

During

Slow down. Eager, anxious negotiators talk too fast. Confident negotiators speak slowly and deliberately. They are carefully watching the reaction of the other party to every word they say. They take longish pauses. They are comfortable with silence, so when asking or being asked a question they take their time.

Cross-Cultural

As we negotiate across cultures, the differences in how we use language become more obvious and important. This is because a negotiation process is based on a series of agreements which, traditionally, are signalled by 'yes' or 'no' (two words that feature in the titles of approximately half of all books on negotiation). The trouble is, different cultures use these words differently. Low-Context Cultures (very broadly, Western Cultures) freely use these words to signal agreement or rejection. High-Context Cultures - particularly Face Cultures (where 'saving face' is valued highly) - are much less likely to be so confrontational with their communication. They are much less likely give a direct 'no', and 'yes' could mean 'I understand' not 'I agree'.

Similarly, we are often seeing negotiations between Non-Negotiating Cultures (generally, Western) and Negotiating Cultures (for example, East Asia and Middle East). In such negotiations, the former report becoming very frustrated because the person from a Negotiating Culture "would not take no for an answer!" Every time they met after they thought they had an agreement, the other person was asking for the same concessions. Of course, this was not their 'fault'... it was their culture.

In such communications, your use of voice - particularly inflection - can add powerful meaning. Here are two examples:

When asking for agreement, ask 'yes?' with a strong upward inflection to your voice. This makes you seem less threatening and encourages them to respond. (You still may not get a 'yes', but you'll probably get a nod.)
When giving a 'no' say it with a strong downward inflection. Any statement said with a falling inflection will be perceived by the listener as more authoritative and final.

People are much more likely to believe how you say something than what you actually say, so you need to think, "What message do I want to give here?" With a little attention - especially to the areas of rate of speech, pauses and inflection - you can make this a powerful ally in your negotiating.