Anno 1800 gets pretty complicated as the game progresses, and you will want to take advantage of every inch of land on your islands. You will also need to build as efficiently as possible, to avoid wasted time and money. Saving both space and money is the hallmark of a good layout.
For cities, a good layout will normally concentrate the services that citizens need in the center, and then surround them with residential buildings. This allows a large percentage of the population to benefit from those services, and you won’t need to build multiples of the same type of building to cover all the people who live in your city. This cuts down on maintenance costs, as the buildings like Pubs and Markets don’t have a limit on how many people they can serve.
For examples of the city layouts be sure to check out the Anno 1800 Wiki. It’s a really good resource, as people can upload plans for layouts that the rest of the community can then try.
Production Building Layouts
Production Building Layouts work a little differently to city layouts. What you are trying to do here is make the best use of space, but also have the shortest distances between the different parts of a production chain. Yes, you can have storehouses that are all interconnected, but you lose a lot of time as your workers travel between the production point and the storehouse. This normally means putting related parts of the chain very close together and needing to use the Blueprint mode to really plan ahead. It also helps immensely always to consider the input and output of each building, and meet new needs in clustered buildings as those needs arise, rather than trying to plan ahead when you don’t have access to certain building types.
Once again, a great place to go for examples is the Production Layouts section of the Anno 1800 Wiki; it is filled with great examples from other players.
Keep in mind that, depending on the difficulty level, you can simply demolish or move buildings that end up being placed incorrectly. You can do this for free on Normal difficulty, with an increasing cost or penalty as the difficulty increases.