No time to mince words, world orders must be destroyed.

The games works like this: Two opposing sides can only meet through the exchange of thermonuclear weapons.
When you first start, identify which country you are strongest in. If you have an equal number of armies on each, identify your strongest position.
If you are close to a president or launch code, take it, but don't be so weak that your opponent can sweep in and take it back.
You can certainly attempt to take out your opponent the old fashioned by maintaining armies in their country and trying to get bonuses to take them out from within. It is possible to win this way.
But to ensure success, eliminate your opponent from your country. This will force them to engage in an arms race, working their way up the missile. If you still have armies in their country, you can wreak havoc from within. If you have been expelled from their country, you must work your way up the missile. Make sure you have +2 bonuses AND have access to a spy. The spies will be your only lifeline in the event of a nuclear strike.
The spies can bombard the foreign president and launch code preventing a nuclear strike. This is your last resort, if you fail to avert a strike, its over. There have been no reports of a player surviving a nuclear strike. Also, spies can take out the scientists, which are often left unguarded. Keep this in mind. In fog-of-war games the spies are valuable in that they can see the president and launch code and gauge the likelihood of a nuclear attack.
Do not leave any armies on the nuclear launch territory, they reset to 15 neutrals at the start of the turn. Its use it or lose it once the button has been pressed.
Good luck, and post your strategies here.