The biggest drains are typically the rear LCD/Live View and any wireless features such as Wi‑Fi, Bluetooth, or GPS. Built-in flash is also a major power user; avoiding it can noticeably increase shot count. Video and Live View use the sensor and screen continuously, so they drain batteries much faster than shooting through the optical viewfinder.

Autofocus and lens image stabilization do use power, but mostly when actively engaged. They usually matter less than LCD/Live View, flash, or wireless features. The simple idle/on state is a relatively small drain.

So, to maximize battery life:

• avoid Live View/video when possible
• reduce LCD use, including image review after each shot
• turn off Wi‑Fi/Bluetooth/GPS when not needed
• avoid the built-in flash if possible
• use the optical viewfinder instead of the screen

Turning the camera off between shots usually won’t make a huge difference over short gaps, since idle draw is minor, but it can still help and most DSLRs power up quickly. If you’re trying to stretch a battery as far as possible, switching it off during longer pauses is worthwhile.

Also note that official shot counts are often based on CIPA-style testing, which includes flash use and power cycling, so real-world battery life can vary a lot.