Negotiation is the most important aspect of Diplomacy, but is the hardest to master. Great negotiation skill comes from experience.
Before opening negotiations, be sure to have a plan for yourself, as well as a plan for the power or powers with whom you are negotiating. Without a plan, negotiation does nothing except damage your reputation when you are unable to live up to the promises you made.
Negotiation is divided into these categories:
- 1. Attack a power
Attacking any power requires assistance. Show the advantages, and make sure that you divide pretty equally between the country's supply centers. It's pretty safe to be generous with another power's supply centers. However, be generous to a degree - be too generous, and you soon will see yourself as everyone's ally, creating suspicion.
- 2. Non-aggression pact
If two powers have an unhelpful stalemate line, they can sign a non-aggression pact to clear that stalemate line or not to attack each other when either has an enemy to deal with. Beware though, somebody can still stab you seeing that you are empty.
- 3. Prevent certain alliances
If playing Turkey, the last thing that it needs is a strong Austro-Russian alliance, as it could crush Turkey's chance. If playing Austria, you should do everything to stop at least two countries to attack you in the first few years. As England, a Franco-German alliance would be disaster. This way, preventing certain alliances is necessary to live - even alliances on the other side of the board can hurt later in the game. A common method is to create distrust between two countries that seem to have an alliance. If Austria wants to break the alliance between Russia and Turkey, then Austria could tell Russia what Turkey might do to stab Russia, and vice versa. After enough of this, Turkey and Russia will not be so willing to help each other, which will be better for Austria.
- 4. Prepare for a stab
If you have a very loyal ally, you can negotiate so he completely empties of units the supply centers closest to your territory, while you prepare to take them. This means that a short time span you can take his supply centers and cripple him before he can react.
Furthermore, try to make it so your stab has immediate results. You should be able to take at least a supply center or two in the next fall. Unless he is much stronger then you are, this gives you the advantage over him, and means you might be able to avoid a counter-attack.