I guess pointing even more antennas to a star which is detected to have earth-like size and location (SETI like programs). With even larger telescopes - checkin

I guess pointing even more antennas to a star which is detected to have earth-like size and location (SETI like programs). With even larger telescopes - checking the light spectrum of the planet reflected light for chemical check of the planet (reflected light spectrum can show what the source is made from, to some extent).