1. Call in (or use the online live chat) to sign up for your new service. They will tell you to go to your local comcast store and buy a self-install kit. Don't. They will tell you to call in to tech support to speak to someone when you do the self-install. Don't.
2. Just plug in your cable modem, router, and computer.
3. Open a web browser. Any connection you try to make should automatically be showing the Comcast self-install page.
4. Click through various obvious prompts until it says "Activating... (please wait 10 minutes)". Wait for a long time. For me, this page never moved on, so if that happens to you proceed to the next step :
5. Close the browser and re-open it. You should get a prompt about "resume activation in progress". Select "create a new login" and fill in the blanks.
6. You will now to get a page that says "continue to download the Comcast desktop package" ; there's no option to not do it. Go ahead and click continue and you will get a download popup window with the "Run , Download , Cancel" options. Hit Download or Cancel (not Run!!), and then just don't install it. This software is nasty malware that tries to install a toolbar and change your home page and all that shit.
7. Close the browser and open it again - you should now be live on the net.