Asslam o Alaikum

After passing the written test of the below mentioned posts, today I have received the call letter for interview in Trade Development Authority of Pakistan for the post of Trade Development Officer/ Project Implementation Officer.
Now i would like to request the senior members of the forum kindly guide me for the preparation of the said interview, it will be held shortly i have less than a week time. i have not given interview before so i am little bit perplexed and confused.
In the light of above, please guide me for the better appearance.

Thanks and regards

Prompt response is required please.... please.