Body language goes both ways, Your own body language reveals your feelings and meanings to others. Other people's body language reveals their feelings and meanings to you.  

How do we show confidence, intellect and suitability during an interview through our body language? 

They say before an interview instead of having your head in your phone or frantically reading over notes, you should do the "Power Pose". Stand with your feet apart and arms out making yourself as wide as you possibly can, try to avoid doing this in the lobby before your interview.

This action increases Testosterone and Cortisol levels significantly, getting you pumped for your interview. 

During your interview, be aware of your body. Sit up straight, this not only helps you concentrate but makes you appear bigger which demonstrates power, like a peacock. 

Leaning forward when answering questions shows that are ready to face any question and challenge directly and readily, moving back shows fear and hesitancy.  

Gesturing with your hands when answering a question demonstrates an in-depth knowledge of the subject. Some political figures use hand gestures to send signals of authority and power during their speeches. Having your hands visible also shows transparency.  

My key tip in an interview is to smile, it naturally relaxes you and makes you seem confident, trustworthy and likable.  You are more likely to be remembered when you're smiling.