How can I impress people with my skills for the first time and how to maintain them?

In an interview, first impressions matter.
There is research on how people form opinions about you in the first 30 seconds.
This means that how you speak, how you enter the room, and how comfortable you look are really important.
Speak clearly but slowly, walk with confidence, and think through what "props" you carry so you don't appear over-cluttered.
http://www.psychologytoday.com/collections/201203/the-first-impression/first-glance-0

Hi Thaer, as the above answers say - both communicating hunger/drive and making a great first impression is a good start.
However I notice that your question is posted under 'Graphic Design' so I am assuming its related to showing your skills in that domain.
The best way to communicate how good you are at your skill (designing, conceptualizing, editing etc.) is to carry a well maintained portfolio of your work.
Whether you work in creating written content or visual, you can carry samples of your work when you go for an interview.
Also make sure these samples are also available online on your online profile.
Add a link to your video CV with a demo reel, add links to your Tumblr account with your works- these are just some ideas.

In your field, you can start by showing your graphic designing skills in your very own CV.
Do not opt for a plain template; instead, add your personal touch by using colors, graphics and anything else that would reveal to the employer just how creative you are.
During the interview, be self-confident and very well aware of the company's work and the job role you're being interviewed for in order to show your interest and leave a positive impact.

The key to making recruiters love you is preparation.
You have to be prepared — to know your strengths and build on them.
You also have to show enthusiasm (28.8% of recruiters in the MENA region choose hunger, drive and ambition as the most important thing to them when making a hiring decision.).
You can also increase your chances of landing your dream job by avoiding these common interview mistakes: http://www.bayt.com/en/career-article-562/.
Good luck!

firstly i must smile them&i try to convey my answers in direct eye contact