Make Sure Every Single Candidate is Treated Like Gold - so many startups I know don't do this one, but it's actually pretty big.
Here is the concept. No matter what, every single person that ever interviews, or for that matter touches your company in any way, should have a great experience, regardless of the outcome of the interview.
People talk, text, twitter and update their status on FB and word about how you treat people WILL get around.
Once I know from other people in the company that it is going to be a "no" for someone, I switch gears from hiring to “successful exiting of the candidate.” The goal is speeding up the process of getting that person out of the building so it prevents wasting the time of the engineers while making sure that person is respected and treated just as well as anyone who a “yes.”
I always pinch myself to remind me that it is critical that even when we want to end the interview immediately (which happens) we do so in a way that is honest, respectful and mindful that we want that person to go away feeling like maybe they are bummed the interview didn't work out, but that the company rocked.
If you do this, believe me it will get around and it will benefit you in many ways. If you don't do this and you act like a pompous ass in the interview, it will get around even faster and it will cripple your ability to hire good people.
I bet right now, off the top of your head, you could name at least one company that has a reputation for treating candidates or its people like shit. That news travels fast and far.
I know that I have jokingly said that C-level candidates should be killed, but in all seriousness, when any candidate comes into your office, make sure your shit is together, you're organized and you take extra time to give respect to the people you say “no” to. If you do say “no,” tell them exactly why you are saying “no.” Don't bullshit them and don't simply blow them off... it will come back to bite you. One of your key evaluation metrics for your HR person is what percentage of people come away from the interviewing process loving the company. A second one is verifying that every single applicant and interview candidate has been responded to.