Prolong Your Nintendo 3DS' Battery Life

Many people are frustrated that the Nintendo 3DS has a shorter battery life than its predecessor, the Nintendo DSi. Here's how you can fix that.

Steps

Adjust your 3D depth slider. Facilitating 3D visuals consumes quite a bit of power due to the increased backlight and transparent LCD. It is most efficient to forgo the 3D altogether.
Adjust your brightness. As with every other handheld device, the brighter your back light is, the more battery power you're using. When you are outside in the sun, switch your brightness to 4. When you are inside, switch it to 1-3.
Turn off your wireless. Only turn it on when you need to use it (System Update, eShop, StreetPass/SpotPass, etc.).
Use headphones. Using the speakers uses more battery power. Using an external source, less power is used. Make sure you don't use a headset with a microphone, as this will result in audio feedback.
Use the charging cradle. The Nintendo 3DS battery is designed to be charged frequently. When your system isn't in use, you should place it on its charging cradle. That way, your system will be at full charge when you pick it up again.
To avoid the 3DS losing power while in sleep mode, place it on the charging cradle.
Play for short periods of time to avoid damaging your 3DS and/or eyes.

Do not leave 3DS in the sun as it will overheat and break.
Don't use the 3D feature all the time, as it will eventually wear the battery out.
Don't leave your 3DS near younger siblings, as if they are under 6 it may damage their eyes, and they may chew on it.