First of all, I think that we should start sending out a signal as soon as possible because with the economic and enviromental problems going on, it would be nice to have some intergalactic guidance.

As for the message inside the signal, I think that we should include something along the lines of:

"Hello fellow beings. We come from a planet called Earth. We live in a star system called "The Solar System". We are on a quest to find life among the cosmos (another word we use for stars). We seek peace among the universe. Any reply signal or message would be very appreciated."

Also, the message would be encoded in a numeric sequence that when decoded, would show the message and a picture or earth, man, tree, and a peace sign.