If you are using external speakers, place the speakers away from the laptop microphone and turn down the volume to a comfortable level.
For those who have external microphones, move the microphone about a foot away from the speakers. Avoid typing on an unmuted microphone, and step back from the laptop when using hands-free mode. You can also reduce the microphone volume level by 50% or less and reduce or turn off the microphone boost option.
Some computers have an echo cancellation feature, but it could be compromised on high CPU load. Closing few processes will help enable that feature.
If none of these options are successful, use a headset or headphones instead of speakers. This is the easiest way to get rid of an echo.