Make sure to keep eye contact, dont swing side to side on chair, always try to answer questions as professionally as you can. and if they at the end of the interview ask if you have any questions for them, do it, even if u have nothing to ask them just think of something and ask them question thats related to that job position. Just because you ask or dont ask question at the end doesnt mean u will or wont get the job. I mean, i got my job without asking question at the end ( idk how) i guess they just felt sorry for a subhuman ( it is retail job tho so eh idk) but its good thing to do because it shows you are willing to work the job/ confident in the job/ have motivation/ want to know more about company/ position.