I think that the way you speak can determine the first impression another person has on you.

 Saying Goodbye or Hello is not only used when you are making new friends or giving any interview. It is considered as a good practice and helps in enhancing your communication skills. E.g if you had a long conversation with a person in a party and you left without saying good bye then that's not good and considered as a bad manner. That person might think that you have some kind of attitude problem or you didn't enjoy his company. When ever you great some one always Say some thing like "Hello nice to meet you" and "Goodbye i have a wonderful time with you"

 Good manners is the key to making friends and even getting a good job. The more friends the more good network.

 YES! Also the way you dress, the ay you talk, and the way you act.

 How you say, and phrase, and answer everything reflects on who you are, your nationality, your personality, your being. I agree.

 It's polite to say hello and introduce yourself and others. In the job situation it's very important to look them in the eyes and shake their hand firmly but not to hard and introduce yourself and why you want the job. Just as important is the way you say goodbye. People need to know they are welcome in your home.

 It absolutely does.... You can "ready a lot about a person by the way they say those things.

 Totally...Saying hello really...down and sad...tells people that you are not a very happy person. It's like the expression..."First Impressions count" its technically the same.

 Yes it tells people if you have manners or not!

 Yes it costs nothing to be polite yet some people forget there manners and are either miserable or seem to think there so important they don't need to use them i heard within 2 minutes of meeting someone they get a profile in there head of you if this is true we need to take the time to care be polite

 Saying hello and goodbye tells people a lot about you because maybe you said it very rudely. Then that person would infer that you are rude so always be polite when saying the simplest things.

 Saying hello or goodbye can make friends, get one into a job, get you out of a sticky situation and is common respect that can be used to accomplish many things.