I generally follow a fairly balanced research plan, focusing most of my energies onto land based military techs (cannon and infantry). Once I get up to about 4 universities I'll generally have 2 going military tech, one industrial, one enlightenment, and then I can use my improved military to conquer more land and get more universities for even better learnins.

If my military tech is ahead of other factions enough to be significant, then not too many people can put up a good argument against me with a bayonet up their posterior.

Naval I do research a bit of, but don't focus a high amount of energy on, as the seas in Europe are generally fairly calm, and most conflict happening in the Caribbean. I can generally stand to have my Caribbean fleets hiding in port until I can get fleet re-enforcements out there to beef them up, or a dockyard built there for a bit of on the spot re-enforcing. In Europe, my general plan of attack is to take out a country's port provinces first and foremost, which will cut off their navy from supply. After that it's just a numbers game, that I will win so long as my land forces can hold the line.