Buying a used TivoHD...

[plazman30]

What will I need to do when I get the unit up and working for me?

[pdonoghu]

You will need to connect it up to a signal source, cable and/or antenna. You will need to connect it to a phone line or network. Then run guided setup so it knows where you are and who your provider is to get the guide data. Once that is done, call Tivo customer support to add it to your account, or create a new account. You will need to subscribe it to the Tivo service for it to work, minimum of one year commitment. Various subscription plans are available. Then sit back and enjoy.

[worachj]

Do a delete and clear to reset your box back to the factory settings.
http://support.tivo.com/app/answers/detail/a_id/368/kw/selling/r_id/100041

Register for service
http://support.tivo.com/app/answers/detail/a_id/29/kw/register%20for%20service/r_id/100041

Getting Started with HD TiVo DVRs
http://support.tivo.com/app/answers/detail/a_id/73/c/105/r_id/100041

Lean about TiVo features
http://www.tivo.com/mytivo/howto/index.html