Forget min-maxing, just do what you want to so long as it doesn't break your country.
My aim is to be gandalf, but there is no gandalf, avatar here... Some time ago it was to be elf(when i was very young and very stiupid), but decided that istari is more awesome.
So, now you are not young anymore ....
First the basics: always build CoTs in coastal provinces because they give an extra fractional colonist. Make sure they're in fairly central, easily-defensible locations. Most importantly, only build them in provinces where you have a core.
The benefit of building lots of CoTs is that each one gives a pretty substantial bonus to the income of the province it's in, quite apart from its trade value. The downside is that each CoT you build needs you to spend money on sending out more merchants, and the global number of merchants you have acts as a penalty to your compete value. Some players like to just build one CoT for all their empire, and gloat as its trade value climbs into the multi-thousand ducat range. Personally I prefer to set up one in each major region. If you build one in the centre of the American East coast - Manhattan, say, it will probably cover all your american colonies. If you see that your provinces in the Caribbean are trading through somewhere else, you'll know there's room for another.
As trade values increase overall, AI countries tend to set up their own CoTs, so late in the game there are lots of small ones instead of a handful of large ones.
Thanks again for the reply Stephen, I greatly appreciate your help.
Just a few more question for the day and I'll be on my way.
What buildings should I build in the colonies? Just trade and ignore tax and production based ones since the colonies don't generate tax (Hope I'm right in thinking that)?
Are the building that cost around 1500 ducats worth the money? I'm talking the likes of factories and Universities.
Finally, I'm going to declare war on the Creek. Should I defeat them and force a change in religion to reformed (my state religion) wait till the truce expires and go in for full annex or just Annex them straight away and change religion through missionaries?
Here i completely NOT agree on. I think that this +0,1 colonist won't save you anyway. Best is to build cot in high manpower province like thrace, london, paris, moscow or so. It is because every COT level increase you manpower by 10% which mean, more manpower you got in the province, it is more COT worthy. I think think that, Kiev is also a good place for COT, but most people don't build it there. Ofc, if COT has big manpower, and is on shore, it IS good, but it is not like it will matter so much. Anyway i think that best is to also consider that there is event for grain provinces that increase their manpower or tax, so grain provinces are most COT worthy. Anyway if you plan building COT on america i think it does not matter so much where you build as all colonies got quite low base manpower, which means building COT in shore province is good idea. If you plan to move yourself just only into america, and sell your continental provinces, it may be a good to build cot in place like manhattan. As i suppose, your fleet will be big, you will be able to easily defend it from any attack by that, even if your armies will take looses.
that one about Kiev
Actually it's a great place. Any inland grain provinces with base tax over 10 are wonderful CoTs, they can get the agricultural revolution for extra tax, and the more value of the trade center, that tax can into space.
Yeah, i was sometimes wondering if not move COT from moscow to kiev instead in my russian games.
I would suggest keeping both of those but dumping Novgorod.