That's the most loaded question of the week. It's hard to answer for two basic reasons: it's different on different ships, and people want different things.
1. Some say book midships because it's smoother.
2. Some say book near the elevators to cut down on walking
3. Some say book away from the elevators to cut down on crowds.
4. Some say book high for the view
5. Some say book low for the stability.
It goes on and on. Individual ship deck plans show where the biggest cabins and suites are, if that's what you're looking for. There's no rule about this. Best you can do is specify a ship and ask here, and you'll get lots of opinions.