Believe it or not, some candidates get way too informal—offering bear hugs, fist pumps, or chest bumps after the interview. Others will ask the interviewer to grab drinks after work or become friends on Facebook. You want to connect professionally, but not nearly as informally as these actions suggest.
Criticizing former employers
Never trash-talk your former employer, no matter how temping. Nothing good will come of it because recruiters wonder if you're criticizing the old boss, might you do the same about them?
Mistreating the receptionist
Everyone you encounter—from the security guard and front desk receptionist to the recruiter and hiring manager—will have a say in the process, so treat everyone with great respect. Assume you're being watched and judged from the moment you enter the offices.
Skipping the thanks
Not sending a thank you note after an interview is just as bad as sending one with typos or mistakes. Don't be generic; customize the note to reflect the conversation and to share additional details that build on the discussion.