Courtsey: MangalDosha.com

Manglik Dosha - What to do - Upayas:
The Mantra given in the Purana is:
Dharanee Garbha Sambhootham Vidyut Kantha Samaprabham ||
Kumaram Shakthi Hastham cha Mangalam Pranamamyaham ||

Here is Mangala Gayatri Mantra:
Om Veeradwajaya Vidmahe Vighna Hasthaya Dheemahi. Thanno Bhauma Prachodayath.

Cryptic Mantra: Om Kram Krim Kraum Sah Bhaumaya Namah ||

General Mantra : Om Am Angarkaya Namah ||

Any one of the above given mantras can be chanted for a fixed number with concentration. 
Total number of chanting of this mantra = 10,000 times starting at 8:00 clock in the morning. 
In Kaliyuga it's been recommended to double the amount of all mantras so I will suggest to 
do it 20,000 times. 

My best advice is to get help of a learned pandit, brahmin or the astrologer preferably from 
your local community.

Meanwhile if you're feeling pressure or stress please use Shree Mangala Chandika Stotram. 
It's the best remedy. If possible recite it every morning and evening, especially on 
Tuesday(MangalVar) after bath(snan), it's best to do one full mala, ie. 108 times of 
Shree Mangala Chandika Stotram.

Write down Shree Mangala Chandika Stotram from our website or download picture of it.