Do not use a laptop on a soft such as a bed, couch, pillow or even your lap.  Doing so may block the vents on the bottom of the laptop, causing it to overheat, which will cause any heat sensitive part to fail. Some parts like the hard drive are not that expensive to replace, but your personal files, pictures & documents may be lost.  Other parts like the motherboard are not economically practical to replace.
If a hard surface is not available, use a TV tray, cutting board, large book or other flat surface. Laptop cooling plates with a fan are also available at most stores that sell computers and computer accessories.
You should not stack things on a laptop computer, as the pressure could break the LCD screen. A new screen can also be very expensive to replace.  When placing a laptop in any bag or luggage, disconnect or remove all devices that are plugged into any external port.  Mouse, wireless mouse receiver, wireless network adapter, etc.  Leaving them connected can damage the device and/or port.
If you leave your laptop plugged in and the cord is not concealed, be careful not to trip or pull it.  This may damage the cord, laptop power socket or the entire laptop if it is pulled off the table or desk.