If you wear a tie to an interview, do not take it off during the interview.  If you wear a jacket to an interview you may take it off, but then, it might just not be prudent unless it is very much too hot for you in a room.  Disrobing is just not a very professional way to conduct oneself in an interview, even if the interviewer is wearing sandals and a t-shirt.

Certifications.  They’re great.  But regrettably “Paper MCSEs” and others with no skills have ruined the party in a way.  Be prepared for each paper certification that you have to back them up with real-world experience and justification to the paper.  Many interviewers will let you get by with the paper alone.  But not savvy IT pros, so be ready…