Here's my advice: write the novel that you wish someone had already written at a time when it would have been really useful for you to read it. Also, have the ending in mind first and figure out a way to start it so that the ending brings you full circle back to whatever was happening at the beginning.
Sibel Edmonds novel "The Lone Gladio" was an interesting read. It wasn't that difficult to work out who the major villain was based on. I'm not so sure who some of the minor villians were, but you may know. And just how much artistic licence was used? Maybe not that much?
You might find John le Carre’s novels helpful.
Here's my advice: write the novel that you wish someone had already written at a time when it would have been really useful for you to read it. Also, have the ending in mind first and figure out a way to start it so that the ending brings you full circle back to whatever was happening at the beginning.
Sibel Edmonds novel "The Lone Gladio" was an interesting read. It wasn't that difficult to work out who the major villain was based on. I'm not so sure who some of the minor villians were, but you may know. And just how much artistic licence was used? Maybe not that much?