Its a known fact that people are quick to judge you few seconds after meeting you.In less than one tenth of a second of seeing someone for the first time,our brain processes information about the persons face which leads to quick conclusions about the persons qualities.
Although it may be misleading,but first impression do form peoples view about a person.That's why its good to make a good first impression whether you are going for a date or going for an interview
Its important to know where you are making a good impression because context matters.it gives you cues as to how to dress,look and behave..are you going for a date,or you have a bank interview.?If you have a bank interview,you will likely show up in a suit.You should choose attire,grooming habit and conversational style that fits the setting you are going to.
Attitude also matters.Create good attitude by smiling, maintaining eye contact,sitting without crossing your arm or legs.
You can check for more tip on the internet. There are tons of self help books floating online.