Main Points (thanks to Tanya B!)
The basic viewpoints are “first person”, “third person limited” and “third person omniscient.”
Past and present tenses are pretty interchangeable. The only time the reader will notice is if you switch between them or if the reader is used to one and starts a book in the other. The default in most genres is past tense.
Omniscient changes viewpoint within a scene, usually paragraph by paragraph. Unless you have a good reason, default away from third person omniscient.
Body hopper omniscient shows everybody’s thoughts and feelings. It builds a reader expectation that they will see from everyone’s perspective so it is difficult to hide information from the reader without breaking the illusion of the story. It gets very complicated very quickly.
Hidden narrator omniscient feels like someone is sitting down and telling you a story. It takes a few steps back from the characters, showing fewer thoughts and feelings. This creates distance from the reader so it can be harder to engage the reader in the beginning.
Speed of Dark by Elizabeth Moon – Switching between past and present effectively
Dune by Frank Herbert – Body Hopper Omniscient
The Lord of the Rings by J.R.R. Tolkien – Hidden Narrator Omniscient