Cats communicate mostly by body language. Primarily, there is no secret animal language. Behaviorists can read cats like a book!
Cats are often skittish. It needs to see you as unthreatening, and get to know your scent. Even then, if it happens to be feral, it may get close. It might possibly let you pet it. But it will always be unpredictable! The social cues for cats are set at an early age. Feral cats are very rarely tamed! Be very careful!
That said, your best points to consider:
Don't make anything that sounds the leasr bit like a hiss or spit. If your speech is very sibilant, you may consider vocal silence. A few tongue clicks, perhaps.
Avoid prolonged eye contact. As soon as your eyes meet, divert your gaze just a little and make a slow, tight blink. In cat language, this shows you do not see it as a threat.
If you approach, do so slowly and cautiosly. If the cat seems nervous, relax your posture, slow blink, and touch your face (the cat will see the face touching as cat bathing), then change your course.
Try to approach indirectly if at all. It is better to let a cat come to you.
If the cat takes the same path frequently, walk thw area when the cat is no around. It will leave your scent and the cat will have some familiarity with you.
What people are taught as body language of being excited and non-threatening is mostly what cats take as a threat: wide eyes, direct eye contact, prolonged stares, vocalization, forward and engaging posture.
Read up a little on cat body language. You don't need a spell.