Pitru

http://en.wikipedia.org/wiki/Pitru_Paksha

The word 'pithri' literally means father, but it refers to all one's anacestors. According to our mythology, the dead mortals will reach the abode meant for such souls, if they have had virtuous deeds to their credit. All such manes absorb with the seven deities there, named 'Pithris'. The names of these deities are

1. Kavyavaaha, 
2. anala, 
3. Soama, 
4. Yama, 
5. Aryama, 
6. Agnishvaaththa and 
7. Barhishada. 

It is for the purpose of securing a place for parents and themselves as well in this abode that people observe penances and practice several austere procedures.

http://www.wisdomlib.org/definition/pit%E1%B9%9Bloka

“Om Devatabhya Pitribhyascha Mahayogibhyeva Cha

Namah Swahayay Swadhayay Nityameva Namo Namah”

This mantra should be recited while performing all kinds of remedial acts such as offering 

1. Pind Daan, 
2. Gaya Shraddha or 
3. Pitri Bhog to free oneself from Pitri Dosha.

There are 99 days in total for making offerings in a year (

1. 12 death tithis, 
2. 12 Amavasya, 
3. 12 Purnima, 
4. 12 Sankranti, 
5. 12 Vaidhriti Yoga, 
6. 24 Ekadashi and 
7. 15 days of Shraddha). 

Vidhana
http://www.uttaradimath.org/web/index.php?option=com_content&task=view&id=772

Tube
http://www.youtube.com/results?search_query=Pitru+Paksha

Do’s during the Pitru Paksha

During the Pitru Paksha period one  should perform fallowing things.

• Must perform offering food and Tarpan rituals.
• Perform Dana (charity).
• Worshiping the deit.
• Daily prayers like Sandhya and japa.
• Fasting on Ekadashi.
• Agni Hotram (Havan/ Homa).

Don’ts during the Pitru Paksha

Fallowing things are strictly prohibited during the Pitru Paksha

• consuming any meat, alcohol and other intoxicants.
• eating onion, garlic, outside food, processed foods, drumstick, etc.
• buying and wearing new clothes.
• getting a hair-cut.
• performing weddings, Katha and Jhunda, Sacred thread ceremonies, and one cannot move into a new  house.
• starting a new job.
• starting a new business venture.

Reading Garuda Puraanam, Nachiketa story and Ganga Avataranam considered auspicious during this time.

http://www.astrospeak.com/slides/24-dos-and-donts-for-pitri-paksha-puja
http://www.astrospeak.com/article/mahalaya-pitri-paksha-dos-and-donts

Slides
http://www.slideshare.net/search/slideshow?searchfrom=header&q=Pitru