Buy an energy-efficient laptop. The size and type of portable computer have a big effect on your battery life; opting for a smaller screen and a solid-state drive will save power. Check out the power ratings when buying a new machine; and if you can get an upgrade on your battery, it’s worth the splurge.
Use your computer’s power-saving settings. Whether you’re on a PC or a Mac, your computer should come with energy-saving settings that will dim your screen after a certain period of inactivity and turn off your screen and hard drives after a longer period. You can make the length of time your computer stays on while inactive even shorter to conserve more power, too.
Shut off devices and programs you don’t need. The more your computer is doing, the more power it uses. Shut down any programs that you aren’t actively using or that aren’t absolutely essential, and try using only one application at a time. This also goes for wireless, Bluetooth, speakers, and any USB devices; even that USB mouse draws power. CD/DVD drives also use a lot of juice, so try to run all programs off your hard drive, and don’t keep a disc in the drive because your computer will try to read it every time it starts up.
Go easy on your display. A big, bright, crisp display isn’t always a necessity. If you can, dim your screen and lower its resolution to save power. And don’t use a graphic screen saver; just let it go dark.
Turn off scheduled tasks. Unless you’re working on something you’re very worried about losing, turn off autosave functions. Also, stop any programs from automatically opening, such as autoupdate and virus-scanning programs, and close any nonessential programs you may have open on startup.
Keep your computer at a comfortable temperature. Extreme heat and cold will affect your battery’s performance. When it’s above 80 degrees, your battery will discharge more quickly, and when it’s cold your battery won’t charge well. It’s best to work at room temperature. Also, make sure your computer doesn’t overheat (the fan uses a lot of power) by using a cooling mat, keeping vents clean, and avoiding leaving it on soft surfaces.
Take care of your battery. Though most newer laptops run on lithium-ion batteries, which don’t suffer the “memory effect” that older nickel-based batteries did, you should still fully charge it before your first nonsocket use, and you should let it discharge nearly completely every once in a while so your computer can recalibrate its minutes-left-for-computing clock. You should also make sure the battery contacts are clean; if they’re not, clean them with some rubbing alcohol on a cloth.
Use sleep and hibernate modes. Don’t just leave your computer idle when it’s not plugged in. If you’re stepping away for a short time, use your PC’s sleep mode; if you’ll be away for a longer time, use hibernate, which draws even less power, though your computer will take a little longer to wake up. Some laptops, such as Macs, will automatically enter sleep mode when you close the lid.
source: http://content.dell.com/us/en/business/d/sb360/Howto-BatteryLife-Computer.aspx?dgc=EM&cid=43647&lid=1149177&acd=1749984473
