There are several resources I use:
1. The CD Bardo Prayers: http://www.amazon.com/Bardo-Prayers-Tib ... B0028ER83I
Many teachers have said that playing audio, as a form of prayer, is valid - even if you don't know the prayers yourself.
2. The Tibetan Book of the Dead (Hopkins): This has amazing explanations about zhitro and everything associated with it; you can read aloud from this book, directing your reading to the one who has passed away. The bardo prayers on the CD are also in this book.
3. Here's a commentary on zhitro: http://www.abuddhistlibrary.com/Buddhis ... 20KPSR.pdf
4. If you just want to start right away with prayers, if you're feeling compelled to act immediately (as I would be), I don't know what others here would suggest but I would suggest starting with reading aloud the four bardo prayers here: http://neozen888.files.wordpress.com/20 ... rayers.pdf