Tulsi mantras are usually recited before watering the Tulsi plant, during morning circumambulation, or when offering Tulsi leaves to Vishnu or Krishna.
Simple Tulsi Mantra
Om Shri Tulasyai Namah
For daily worship of Tulsi Mata
11 or 21 times
Tulsi Stuti Mantra
Om Vrindayai Tulasi-devyai Priyayai Keshavasya Cha Vishnu-bhakti-prade Devi Satyavatyai Namo Namah
For devotion and the grace of Vishnu
1, 3, or 11 times
Tulsi Gayatri
Om Tulasyai Vidmahe Vishnupriyayai Dhimahi Tanno Vrinda Prachodayat
For purity, bhakti, and spiritual discipline
11 or 21 times
Guidance
Chant near the Tulsi plant if possible. Offer water gently and never handle the leaves carelessly.