How to take a screenshot in Nokia Lumia 510 ?

I wanted to know, because other Lumia devices have a way to do that but i doesn't work for the 510 . Please help..

I know you can do it because I've found two random screen shots in my photos. I just don't know how.

I got it... Hold the screen lock and the up volume key at the same time. Yesssss got it! :-)