So you've made it through book one of (insert number here). Now what?
Chances are, by now, readers are fairly well-acquainted with your world and the characters that inhabit it. Hopefully, they've grown to love them as well-- or hate them, it doesn't really matter. So they want to see their old friends again. But don't just do the bare bones minimum. (The bare bones minimum, by the way can be put into an equation: original plot - same settings +new characters = sequel! It's that easy!)
The bare bones minimum isn't fun to read, and sincce most fantasy series aren't duologies, you'll want readers to come back (again). Yes, introduce new characters. It'll add depth to your story and help keep it from being boring. Yes, put in new settings. It'll keep readers more immersed in your world. But don't do this at the expense of totally abandoning the old ones. They're good, too.
But make your story interesting. Make it fresh. Make it new. For example, The Well of Ascension starts after where most series end. It's about rebuilding and acting nobly in the face of civil war, but it's about much more as well. The Rise of the Wyrm Lord took a risky move, sending a completely new character into the fray. Not only new to the story, but a different gender as well. This must have presented some interesting POV challenges for Wayne Thomas Batson. Which brings us to...
Point of View
Now, there are several ways to address the POV issue, and none is any more right than the others. There's the first-person view, which is hardly ever used in fantasy (notable examples being The Name of the Wind and Percy Jackson and the Olympians). Then there's the ever-so popular second-person POV. Yes, I'm being ironic. The only book I've ever read that used this POV to any major extent is You Don't Know Me. Not a fantasy, but very, very good. Third-person limited view can be seen in The Underland Chronicles, Harry Potter, and Charlie Bone. Third-person omniscient view, however, is the most commonly used (i.e. Mistborn, The Lord of the Rings, and PENDRAGON, as well as The Inheritance Cycle). Which one's working best for you? You'll have to decide. Though it's not done commonly, a series can switch from limited to omniscient POVs-- here's looking at you, Inheritance.
A Little Pinch of Darkness
Sequels tend to edge toward the darker side of life. This gives a nice way to set the book apart from its prequel, but just remember: a little pinch of darkness will do. Don't get too begged down in the heavy shadows or else your readers will get too depressed to really enjoy the book.
On Poetry and Songs
Use with caution.
Dangle that Carrot!
The second book in a series doesn't need to end with a cliffhanger. But make sure the readers are tantalized by the prospect of another entry in the series. Dangle the carrot in front of their noses, and they'll follow you wherever you go.
Do it tastefully, of course.
Part Three: The Penultimate Novel coming soon!