It depends. If he talks to you first, you dont want to sound extremely happy about it. Sound calm and natural. For example if he says, "Hey" you may want to say "Oh, hi." to start it off. But if you want to text him first, you could start by either 1. Ask him a question you know he would know. About anything, just not about relationships. Or 2. Pretend that you "accidentaly" sent him a message instead of someone else.
You say "hello" in English.
Say Hello to Rosita!
Kamusta is how you say hello
halito is how you say hello and how to say hello how are you is Halito, Chim Achukma?
This is how you say hello in Turkish: Merhaba = Hello
Crocodiles do NOT say hello.
In Neapolitan, you say "ciao" to say hello.
In Paiute, you can say "Kwai" to say hello.
hello hello
Irankarapte - Hello
hello same hello
In Tunisian, you can say "Marhaba" to say hello.