Where can you get halo reach the beta?

Purchase a copy of Halo 3 ODST and go to Xbox LIVE, you will be sent an invitation to play. (May 3rd) You also need a gold xboxlive membership to play it and when you open up the ODST screen you will see it at the bottom in the thingy when you're about to play. It takes about 20 min.s to download and you always need to have ODST in the xbox to play it.

No you dont get sent a invitation sent to u. the beta embedded onto the odst campaign disk! All u have to do is start up halo 3: odst, and from the menu select play beta, then download the beta(it does take about 20min), when it's down start it up.