I am listing down a few points that will help you impress others in just one meeting. Sounds good right? So, let's get started.....
Smile - It's one of the most powerful gesture. Find reasons to smile. Being frown won't help in any way.
Be someone who takes initiatives. Try and get rid of your shyness, irritation, ego, ignorance or whatever is stopping you.
Be proud of yourself but never let that pride harm your relations with others. By this I mean, never be ashamed of yourself and carry that grounded attitude and dignity forever
Be genuinely interested in other people's talks and discussions
Ask questions, rather ask some related interesting questions after analysing a person. This helps the opposite person get comfortable and gives an opportunity to open up.