Say "moin, moin" to him. He may will look surprised when you tell him: "This is the way people living in Germany close to the Northern Sea say "Hello".
Usual way when we want to wish someone good reception say hello or Hi or good day,hey,heyy,hai, holla, ola, whats up, greetings , yo , peace, aloha, hallo,cool,welcome and ciao.