I work for a company that provides wireless security software. We have been looking for a qualified candidate for about 8 months now and we finally got a candidate. Sadly, I don't think he's going to make it to the next step.

Here's  a list of things why candidates have failed:

Do you know what we do?
Did the candidate google us and find out what we do? If he/she has, that shows that the person has taken the time to try and see if he would fit into what the company does.

If the job requirements say a CWNA is the minimum cert, then yeah you need to have a recent cert or at least be able to answer simple, basic questions about 802.11. If you can't answer what the difference is between a bssid and an essid, then you shouldn't be applying for the job. What the ideal candidate would have done is read through his CWNA book to refresh his memory on some of the topics.

If the job requirements say you need linux experience with the command line and logs, then even if you don't have vast experience, you could always join a local or online linux user group, or use linux at home and be able to tell the interviewer more than "ls" when asked what commands you know. If the candidate had taken the time to spend 1 friggin hour with an online linux free command line tutorial, he would have been able to answer basic questions. The ideal candidate would have looked up "search linux logs" and known about grep, more, pipe and maybe even sed and awk. If you want the job then you have to realize that's what you're going to be doing most of the day and the ideal candidate would have known that if he researched what the job would likely entail and would have known at least one grep option.

If the job requirements say sql experience, at least know something about it. Once again, one hour with a free online tutorial would have passed the interviewer's questions.

I guess what I'm saying is, if you want to pass an interview (even if you don't have a lot of experience) then at least come prepared. You prepared for all those certs you have, why not prep for an interview?

The company will list their job requirements and wish list in the job posting. Pay careful attention to this list. Google all the items. If you don't know a subject at all, then at least google it so you can say " I don't know anything about subjectXYZ except ....". Be honest. Tell them what you do know and what you don't know.

If you can ace some parts and know a little about the others on the wish list, you stand a good chance of getting the job. Spend an hour on each of the items in their wish list and not only will be smarter for it but likely have a better pay check.

This is good advice.  I've interviewed people for tech and non-tech roles and this all applies.  If there is something in the requirements that you don't have, you should learn a little.  If there is something that you have/know but don't work with every day, you should brush up. 

Great advice!  I wish I could say it is common sense but after hearing stories from my mom about people coming into interviews in jeans and t-shirts, I am not surprised any more.  Another funny thing I thought was when I re-working my resume to show a more mature and security sound profile, my recruiter reminded me to wear a suit.  I looked at him like he had 3 heads and wondering "Why wouldn't I wear one???"  But its like warning signs, they are there because people don't use common sense. 

I've actually lost out on jobs with startups by overdressing for the interview. Don't just research what they do, try to learn about their culture through such sites as http://www.glassdoor.com/index.htm or Linkedin contacts that work there, friends, recruiter, etc. We pass over candidates all the time where I work that blow the technical questions out of the water because we don't think they will be a good fit for our culture. Wearing a suit to a jeans and t-shirt work environment interview may make you seem stuffy. The rest of this advice is very sound though.

I can understand someone showing up for a job at Arby's in a suit losing points from an interviewer for being over dressed... However, showing up in a suit for an interview for a serious career that requires a lot of education seems standard practice to me.  So I don't think an interviewer could really come to any conclusions on whether someone is "stuffy" solely based on them wearing a suit to an interview, since 99% of interviewees would probably much rather dress casual, and only wear the suit because it's considered standard.

I miss working in a casual environment.  I am in big corp now and I feel dressed down when I am in khakis and a polo.  Then again everyone there is shooting for an exec level job and frankly I can care less about that right now.  I do appreciate the fact that they try to groom everyone into management but at the same time, they have too many of those already and not enough people who actually know how to do anything.  They leave that stuff for the contractors, which aren't always consultants.  At least I can work from home every so often, so I can toss on the shorts, flip flops and t-shirts then and play my music at a reasonable volume.   

I did feel over dressed at my last job when I interviewed, mainly because the hiring manager was sporting jeans and polo, and the IT Director was in shorts and sneakers (summer casual).

Well if they did the OSCP that wouldn't be a problem at all for them, would it ?
I hope you forgive me hayabusa for this remark but I really couldn't resist. 

You're absolutely right. While many people might think that they have to talk their way true it on every job interview question, in fact it's not. Most job interview questions aren't supposed to be answers all 100% correctly.

A great book for coders that could help them is :

http://www.amazon.com/Cracking-Coding-Interview-Programming-Questions/dp/098478280X/ref=sr_1_fkmr0_1?ie=UTF8&qid=1347242932&sr=8-1-fkmr0&keywords=how+to+job+interview+coder+c%2B%2B

I used that book myself to hire people.

Unfortunately (or fortunately in a few rare cases) having general knowledge of concepts in say, SQL, or the searching through Linux logs, is not usually enough for interviews.

I've been to a number of them, through an IT contractor company, where the requirements they gave me didn't quite match up with what the interviewer actually expected.

I mean, Googling a company is fine and dandy, but sometimes they have several different businesses umbrella'd under their name, and so, you can prepare for their core business, but the part of it you might be working for? Totally different and unrelated. Especially (and I know this excuse is older than the dead horse) in this economy. Many businesses have been bought up and just rebranded, while they do their original thing. And sometimes they don't even do the same thing as the parent company, so you can research the entirely wrong business division, and come in cold to the interviewer.

I do agree preparing for an interview is a really great way to wow the interviewer(s), but sometimes I personally feel like not even bothering. There have been a number of times where I researched the company, read up on a couple of the things they said they needed, and then bullshitted my way through the interview because they wanted a completely different set of expertise.

Again, though, this is probably miscommunication between a middle manager at the company, and their contact at the contracting agency, then to me with their gobbled list of things.

Very few direct interviews have these problems, but that might just be from my perspective