I'm giving 1404 a try and found it is critical to settle an island with dates and spices as fast as possible, and soon after, one with indigo and silk, then another with quartz if you didn't luck out and get it with the others.

I'll do the warehouse start to get the best advantage (and, generally, get citizens before the AI), I'll get ship from Lord Whatsisname, buy the gift, go to the Vizier, and send the first ship off into the south fog. Usually by the time the vizier gives me a ship, I've managed to find at least one of the two islands and built a warehouse. The second ship builds a warehouse on the second, I build a bazaar, a tent or two and a woodcutter. At which point, the AI shows up and plops down a warehouse on the far side of one of "my" islands and starts building where I was planning on doing silk or spices, depending.

I don't get it. What do I have to build in order to keep the AI from settling on the island I've chosen? Do I have to fill the entire coastline with markets or what?

Huh. The Cardinal threw a hissy fit that I built on "his" island.

So I can't do much about it until I get nobles? Other than fill the parts of the island I want to build on with markets? If I notice it quickly enough (before he slaps down a bazaar), can I limit him to just the space the warehouse controls with two or three markets?

I've never played 1404, but in one of the earlier ones, 1701 or 1503 can't remember which, what seemed to work to keep the AI from also settling your island was just to build a second market place deeper inland. There would then still be lots of places along the shore where the AI could build a warehouse, but then they never would.

Thanks. I'll give it a try.

I play with no refund of materials so I'm not thrilled with spamming markets before I have some idea where I want them placed, and 9-12 tools at that point in the game is pretty dear (at least for me) but that might be about the only way.