1. Reciting Śrīdevī Māhātmyam: There are three sections in Śrīdevī Māhātmyam - pūrva bhāgaḥ, madhyama bhāgaḥ (contains 13 chapters) and uttara bhāgaḥ. The following schedule can be adopted to recite (pārāyaṇa) Śrīdevī Māhātmyam spread over a period of nine days.
Day 1 - pūrva bhāga; day 2 - madhyama bhāga chapter 1; day 3 - madhyama bhāga chapters 2 and 3; day 4 - madhyama bhāga chapter 4; day 5 - madhyama bhāga chapters 5, 6, 7 and 8; day 6 - madhyama bhāga chapters 9 and 10; day 7 - madhyama bhāga chapter 11; day 8 - madhyama bhāga chapters 12 and 13; day 9 - uttara bhāga.
2. Reciting Lalitā Sahasranāma and Lalitā Triśatī daily. Morning Sahasranāma and Triśatī can be recited (if time permits, archana can also be done) and in the evening pārāyaṇa of Śrīdevī Māhātmyam can be done. Khaḍgamāla can also be recited either in the morning or evening. Recitations during evenings and nights are better during navarātra.
3. Third method is worship different forms of Parāśakti. During the first three days, She is worshiped in the form of Durgā Devi. In the next three days, She is worshiped in the form Lakṣmī and during the last three days, She is worshiped in the form of Sarasvatī.
4. Those who are initiated into Pañcadaśī or Ṣoḍaśī can do laghu navāvaraṇa pūjā during the first nine days and on the tenth day detailed navāvaraṇa pūjā can be done. Detailed navāvaraṇa pūjā can be done on the ninth day also. Morning and evening can be used for pūjā and in the night mantra japa-s can be done.
5. On the tenth day, one should do initiated mantra japa-s to the maximum extent possible.
6. Some also worship ten mahāvidyā Devis during this period.
With regard to the second part of your query, for mantra initiation only utmost devotion alone is required.