general advice

The most important thing to know about modern Lithium batteries is that the "battery memory effect" does not exist. It is a myth and only applies to much older Nickel-type batteries. Fully discharging and charging the battery is completely unnecessary and can be harmful. Modern Lithium batteries can be charged regardless of their current percentage. Other things to be aware of are:

Keep your battery as cool as possible. Heat reduces the lifespan of Lithium batteries. Keep your laptop/phone away from direct sunlight.

Try not to let your battery go below 25% charge as this can negatively impact battery life. The first charge is no different from the 2nd, 3rd or 50th charge. The full first charge is a myth left over from older battery types.

If you won't be using your battery for a number of weeks or months, store your Lithium battery at a 40% charge, and try to store the battery at around zero degrees Centigrade. If you can't maintain this temperature, keep the battery in a cool dark location such as a basement or closet.

Charge your battery often but not always to full capacity each time. It's better to charge it almost full many times than to fully charge it once.

laptop batteries

If you have a laptop, don’t keep it plugged in all the time. From time to time, let it drain to about 50% of capacity, and then recharge it.

Turn off Wi-Fi and BlueTooth if you dont need them running. Most laptops have shortcut keys to instantly disable wireless.

Dont play games, watch films or play music if you can avoid it - all multimedia programs use lots of battery power.

Reduce the screen brightness if you can.

Use Windows power management to shut down the screen/hard drive after 10 minutes of inactivity.

Don't plug in USB devices if possible as these will often drain the battery.

If you are going to be away for a few hours rather than minutes, use "Hibernate" mode instead of "Standby" mode.

Keep the laptop as cool as possible and clean the air vents as often as possible to improve airflow.

phone batteries

Obviously turn the phone off whenever you aren't using it (overnight etc.). This is probably the most effective and simplest way of conserving your battery’s power.

Turn off Bluetooth if it isn't needed - same goes for wireless and GPS if you don't need them on either. Turning these off also keeps you safer when in range of infected phones or networks.

Don't use vibrate, just use ringtone.

Turn off the backlight, or reduce its percentage brightness if you can.

Turn off all applications that may be running in the background on your phone and avoid taking photos as these can drain battery power quite quickly.

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With all rechargable batteries, you have to accept the fact that they won’t last forever, however well you look after them. But you can prolong their life significantly by following the advice above.