First impression is the last impression so dressing comes at very first. Then certain research on the field of the post would helpful in this regard. But if one does not answer with confidence then there are chances that dressing and research are not going to impress the interviewer.
Thanks a lot @jwolf for the tips Man ;)
Let me a share a very famous quote of Bill Gates
If you've found some way to educate yourself about engineering, stocks, or whatever it is, good employers will have some type of exam or interview and see a sample of your work.