I think it's best NOT to accept taxes at all, no matter what. Taxes are permanent, but there are many ways to get rid of boycotts. What I do, is in the beginning, aim to get Peter Stuyvesant in the Continental Congress. Then, immediately build a Custom House. Colonies can be self-sufficient, if you have a nearby ore supply. You can breed your own horses, and make your own tools or muskets. Once the boycotts pile up, merely elect Jakob Fugger to the Continental Congress. By the time you've filled up the European Board with boycotts again, you should be rich enough to pay back taxes on a cheap one over and over again.
Protect the Indians. In every game, one power gets knocked off, and the colonies go to another. If Spanish are left, the Indians are dead. The best way to protect Indians, is to give em guns and horses. They'll tire of horses eventually, and soon they will of guns too, so you won't really get too much for them. But, it is interesting seeing Indians fight back with Armed Braves and Mounted Warriors. If you capture guns with Privateers, just trade em off to a nearby Indian Village.
Use Frigates in place of Privateers. I'm not saying stop using Privateers, I mean you can use Frigates to prey on foreign shipping too. What I do, is only attack one power with Frigates. Its good to keep a friend so you can get rid of stolen goods quickly. But, if your friendly nation is stupid enough to place a Galleon full of goods next to one of your Frigates, go ahead and take it. If you've got Benjamin Franklin in the Continental Congress, you can always make up. And, another thing, keep a scout near another power's colony so you can easily make up with them.
Incite a world war. Not, really too important, but if you're rich, you can have a little fun.
Don't bother with farming. If you've got access to three water squares, just fish.
Always scout. Go to every Indian village, and meet with chiefs to receive gifts. Incas and Aztecs often give big payoffs. And, threaten Incas for gifts, because more often than not, they'll deliver 100 silver to your colony.
It's best to build 'canals', ie. colonies built on an isthmus, so ships can sail between two seas. In the America map, you would be able to build one over Panama, connecting the Atlantic and Pacific Oceans, but it's a mountain square, so you cannot. I also think it is unfair that ships can't sail in Rivers or Lakes. In reality, Rivers played an important part of exploration. The St. Lawrence, the Amazon, and the Mississippi, are important ones to name a few. I made an America Map, where the rivers are now sea squares, you can build colonies inland, that will have sea access.