It's not that hard to figure out, thanks to the useful dropdown menus. The important thing to remember is that you want to expand your sphere of influence without ticking off the Soviets, who in turn are going to push to expand their SoI. Whomever does expand into the other--say, the US giving Cuba favored nation status, or the Soviet trying to set up a deal with the UK--the other superpower can raise the diplomatic pressure. If you're the US, the USSR does the pushing, and you threaten them into backing down, you gain diplomatic points. If they refuse to back down and you do, instead, they gain diplomatic points. If they refuse to back down, though, you can raise the diplomatic pressure with a more significant threat. Now, the diplomatic point losses are greater. I think there are 3 levels of diplomatic threat, as I recall, after which you go to nuclear war. At which point the game stops, because as Chris Crawford, the designer, remarks, there are no winners in a nuclear war.
Hope that wasn't too difficult to understand.
