It's always worth having a look at the System Map of Class M systems...

[Genar-Hofoen]

...otherwise you might miss the odd rarity.

Meet the Earth-like World I found orbiting the Class M star in this system:

 

[Ian Doncaster]

Well spotted. People often do go right past them - my find of the day, just coming back into the bubble, happened to plot a route through a Class M system in Synuefe about 440 LY from Sol, and about 150 LY from the nearest inhabited system ... and got first discovery on an ELW. I'd normally consider myself reasonably lucky to see a system that close in that had first discovery rights available on an ice moon, but people just don't look at the Class Ms.

 

[Ziljan]

As I've always maintained class M are the best stars to look at for pure CR/rank per hour. Simply because all of the juicy HMCPs WWs and ELWs are all within spitting distance of the parent star. They're so close you can usually scan some of them while fuel scooping.