Most laptops have circuitry to prevent overcharging your battery. Leaving your laptop plugged in most of the time should not hurt your battery. It is probably a good idea to completely discharge your battery once a month. Lithium batteries do not have "memory" like the old nickel ones did but fully discharging recalibrates your laptop charge meter making it more accurate.
To stretch your battery turn off everything you aren't using. If you are not using wifi or bluetooth turn them off. Dimming your screen as much as you can still read will use less power. Don't use a screen saver and you can make your laptop power saving options more aggressive (i.e. reduce the amount of time before your laptop turns off the screen, hard drive, and goes to standby.
If you leave your laptop in "sleep" mode a lot consider using "hibernate" With sleep your computer is still minimally running and using a little power. Hibernate saves your laptop's state to the hard drive and completely shuts down so when you power it on it will boot to exactly where you left off your work. I find I have to switch to hibernate because my laptop overheats in my laptop bag.
If you're talking about for when your laptop is in use, for one, you could go into your control panel and make sure that 'battery saver' option is in use.
If you're talking about overall, one thing that can help is preventing overcharging the battery. If your battery is full, unplug it. Another thing you can do is take the battery out when you are near an outlet and solely run the laptop off of power. Since batteries generally only last XXX number of charges, charging it less often usually helps.
yes i am talking abt laptop