The limitations are as follows:
Nothing to do with:
• World War II
• The US Civil War
• The Napoleonic Wars
• The Roman Empire
The only exception would be if said events are not the main focus of the alternate history.
NO political rants! I want alternate history, not Reason #458133 why George Bush Jr.(or any other modern world leader) is the Antichrist (or somesuch). Yes, I hate his regime too, but I don't feel the need to include an Oath of Loyalty to the Resistance in everything I say.
No, political rants are avoidable in AH. Speculating what would happen if horses (or Earth's moon) never existed is hardly political.
One divergence. Add something, subtract something, or alter something. The more you'd want to affect, the farther you'll have to go -- unless we're working with extreme variables (magic, aliens, etc).
My intention, of course, is for us to have fun, isn't that what rules are for? :)