如何正确设置模型，POCO类?

I'm slightly confused on how to properly setup my model. Below you'll see my POCOs and I'm wondering how I can auto increment the ID's and if it's necessary to set the data annotation [Key]. Is there a naming convention of some sort which makes EF recognize the ID/primary key or do I have to use the [Key] data annotation?I'm slightly confused on how to properly setup