1) One who has not yet prayed may not deliberately go to the house of his friend (or to go over to his place in the synagogue) to say “Shalom” or even “Good morning”. If, however, he happened to come across his friend’s house, he may say “Good morning” but not “Shalom” as the name of Hashem is Shalom. (Mishne Berurah 65)

2) If one did not deliberately go to the house of one’s friend, but met him in the street, according to the strict letter of the law one may greet him with the word “Shalom”. The custom, however, is only to say “Good morning!”, so the people will remember that one may not procrastinate with other occupations before praying. (ibid)