How You Talk Indicates to People How You Are
There is no absolute right or wrong in regard to intonation because a case can be made for stressing just about any word or syllable, but you actually reveal a lot about yourself by the elements you choose to emphasize. For example, if you say, HellO, this intonation would indicate doubt. This is why you say, HellO ? when answering the telephone because you don't know who is on the other end. Or when you go into a house and you don't know who's there because you don't see anyone. But if you're giving a speech or making a presentation and you stand up in front of a crowd and say, HellO, the people would probably laugh because it sounds so uncertain. This is where you'd confidently want to say HEllo, my name is So-and-so.