Navagraha Mantras
There are several mantras and remedies for the planets prescribed in the various scriptures. We are giving below the most effective ones as per our experience.

Surya

Surya mantra:
Om hram hreem hroum sah suryaya namah

Surya stotra:
Java kusuma sankasam kashyapeyam mahadutim
tamorim sarva paapghnam pranatosmi Divakaram

Chandra (Moon)

Chandra mantra:
Om shram sreem shraum sah chandraya namah
(10,000 times in 40 days)

Chandra stotra:
Dadhi shankha tushaarabham ksheero darnava sambhavam
namaami shashinam somam shambhor mukuta bhushanam

Mangala

Worship the ruling deities Kartikeya and Shiva.

The Kartikeya mantra:
Om Saravanabhavaya Namah

The Shiva mantra:
Om Namah Shivaya

Mangala mantra
Om kram kreem kroum sah bhaumaya namah
(7000 times in 40 days)

Mangala stotra:
Dharani garbha sambhutam vidyut kanti samaprabham
kumaram shakti hastam tam mangalam pranamamyaham.

Mars is also the remover of debts and the giver of wealth. The following is a highly-recommended stotra of Mars for this purpose.
Angarakoyamaschaiva sarvarogaapahaarakah
Nrishtekargaacha hartaacha sarvadevascha poojitah
Lohito Lohitaakshascha samagaana Kripaakarah
Dharmatmajah Kujobhoumou bhumido bhuminam
Rakta maalyambaradharam shulashakti gadaadharah
Charbhujo yeshagato varadamcha dharaasutah
Mangalo bhumiputrascha runahartaa dhanapradah
Sthiraasano mahaakaayo sarvakaama phalapradam

Budha

Budha mantra:
Om bram breem broum sah budhaya namah
(17,000 times in 40 days)

Budha stotra:
Priyangu kalika shyaamam roopena pratimam budham
Soumyam soumya gunopetam tam budham pranamamyaham.

Guru

Guru mantra
Om jhram jhreem jroum sah gurave namah
(16,000 times in 40 days)

Guru stotra:
Devanam cha rishinam cha gurum kaanchan sannibhaam buddhi bhutam trilokesham tam namaami brihaspatim

Shukra

Shukra mantra
Om dram dreem droum sah shukraya namah
(20,000 times in 40 days)

Shukra stotra:
Hima kunda mrinalaabham daityanam paramam gurum sarv shastra pravaktaram bhargavem pranamamyaham

Shani

Shani mantra:
Om pram preem proum sah shanaischaraya namah
(19,000 times in 40 days)

Shani stotra:
Nelanjan samabhasam ravi putram yamagrajam chaaya martand sambhutam tam namami shanaischaram

Rahu

Rahu mantra:
Om bhram bhreem bhroum sah rahave namah
(18,000 times in 40 days)

Rahu stotra:
Ardha kaayam maha veryam chandraditya vimardhanam
Simhika garbha sambhutam tam rahum pranamamyaham.

Ketu

Ketu mantra:
Om shram shreem shroum sah ketave namah
(7000 times in 40 days)

Ketu stotra:
Palasha pushpa sankaasham taraka graha mastakam
Roudram roudratmakam ghoram tam ketum Pranamamyaham