My idea is... our galaxys main composition is hydrogen right? what if some other galaxy is comprised of another? its logical to think that 1 planet in every galaxy could contain life.. I mean our galaxy alone is almost ifinitely huge... anyway I was thinking... our sun is the only hint of a thing visible from another galaxy right? why not build a HUGE refelective mirror type thing? if some alien species was observing the night sky to the same extent we are maybe there version of "Nasa" would see the reflection? Then maybe they would do the same?
Just a idea that popped up..

and if the aliens are less than friendly stick a huge magnifiying glass on it and hey presto blue peter death ray!

The idea is to listen to incoming messages BEFORE we send any signals out there. Considering what those greys are doing, we don't really want to invite more alliens here.