New England is a relatively small, releasable nation in the Northeastern United States. It consists of the modern-day states of Maine, Vermont, New Hampshire, and Massachusetts. It borders the United States to the west, and British Canada to the north. When released, it contains the regions of New England and Massachusetts. The primary culture is Yankee, with Dixie as an accepted culture.
NOTE: Before releasing New England as the U.S., play as the United Kingdom first and enact the Webster-Ashburton Treaty, which cedes the province of Caribou to the United States. This is to make sure that when you release New England, the region won't be called 'New English New England.' Also, if you chose to release New England before enacting the treaty, then Caribou will still belong to the United Kingdom. This province will then go to the United States once the treaty is enacted, meaning the U.S. will border you from two sides.
With that out of the way, back to the guide. Being released from the United States means you start off with their better technologies, meaning you get a slight headstart on naval technology, among other things. It also means you start off as a Democracy in the New World, which also liberalizes quickly, meaning New England will get more than its fair share of immigrants. However, since the Federalist (Liberal) Party will dominate the Upper House for most of the game, even when Socialism rises, you will need to build up your capitalist base in both New England and Massachusetts. Use your Nation Focuses to Encourage Capitalists in the two regions. This will definetly pay off later on, as all you will have to do is sit back and watch as your Capitalists build every railroad and factory in the nation for you. With taxes, bring taxes on the rich all the way down to 0%. Do the same for the middle class, but only if you can do so without running a deficit. For the poor, raise taxes to the maximum. You'll be getting most of your tax income from the poor (though this is true for any nation), and you need more people to promote to Capitalists.
Your first technology to research should be Romanticism, for two reasons. The first reason is quite simple. The three inventions that you can get from discovering Romanticism total sixty prestige, which can bring you up to at least Secondary Power status. The second reason is to enact the 'Miskatonic University' decision. This is a decision unique to New England, and it gives a 10% Research Points modifier. To enact this decision, you must have discovered Romanticist Literature, which can only be discovered through Romanticism.
For your first territorial conquest, try Denmark. Prussia likes attacking the almost completely defenseless Danes for Schleswig, and sometimes takes the entire Danish mainland too. However, we aren't looking at any of Denmark's European holdings, or even Iceland and Greenland. No, we're looking at the Danish West Indies. Snce Prussia has taken care of the Danish army, declare war on Denmark for the Danish West Indies. (If you can, and if the war is going well enough, use the Repay Debts CB too, as Denmark has probably gone bankrupt from the war with Prussia, and has probably taken loans from your country too, though this isn't guaranteed) Mobilize your forces, since you probably can't build a brigade yet, build some clipper transports (Prussia has been kind enough to take care of the Danish Navy for you, too) and land your troops in Saint Thomas. After occupying St. Thomas, put your troops back in the clippers, and continue to occupy Danish land until they give you the Danish West Indies. Even if Denmark has already surrendered to Prussia, you have no need to worry, because they won't get an army together fast enough to fight your troops. Once you get a high enough warscore, send a peace offer to Denmark, and they should give you the Danish West Indies. Congratulations, you now have your very first colonial possesion! The Danish West Indies are now the New English West Indies! The population will consist of Danish and Afro Caribeno POP's, but they will assimilate into Yankees, and while they'll be ticked off about being conquered, they won't be militant enough to rebel. The tobacco money earned from Saint Thomas will help sustain your economy, and you now have a foothold in the Carribean and Latin America.
(I intend to fill the gap between this and the Civil War eventually)
When the American Civil War breaks out, this will be of much importance to you, as it will give you the opportunity to accquire a high-populated, at least somewhat industrialized state with POP's of your main and accepted cultures. Because the CSA typically forms weak, and because their troops will be occupied fighting the Union, declare war on the CSA for Georgia. Hopefully you will have built up a respectable army and navy by now, so landing troops in Charleston or Savannah shouldn't be a problem. Be sure to take Georgia BEFORE:
A) The Confederacy gets taken over by the North.
B) The Dixie forces manage to score a white peace with the Union, and send Robert E. Lee and Stonewall Jackson, along with their many mobilized troops, to fight your armies.