I had a Java interview scheduled today. I went near the office location and on the way I realized that I was not ready for the interview. The last year at my current job has been a very draining experience due to which I have been unable to polish my skills (no excuses) - which is one of the reasons I was looking for another job in the first place.
On my way to the interview I realized I had not brushed up on my skills for a long time. Previously I have been very good at giving interviews, but this time it occurred to me that it would be a disaster so I just went back home without giving the interview.
Is there anything I should do in order to avoid being blacklisted (if possible)?
I personally would place a phone call or email to let them know that something came up that you weren't able to make it, and that you had decided to stay where you are rather than seek a new position. Thank them for the time, apologize for not being there when you said you would.
Admit it: You're never going to be as "ready" as you want to be, there'll be always room for improvement.
What you did is wrong on multiple fronts, but I'm not going to start criticizing you as you clearly see you're the one with the faults.
You need to do two things:
As of now, for the "damage control", you can call them (or email, but call is preferred) and inform that something unavoidable came up and you were not able to make it to the interview. Also tell them you realized that you were not fully prepared to handle the interview and so to save everyone any further trouble, you did not finally show up. Apologize for the time which is wasted because of you.
Then politely ask for a rescheduling (though it is unlikely you'll get one) and leave it to them.
For future: to ensure this does not happen again, make sure you have your self-confidence boosted before you plan to appear for an(other) interview. That said, remember, it's better to appear and fail than having a no-show.
The first approach will
At most cost you the time and effort to have the interview
You'll gain invaluable experience and confidence.
The second one will
Cost you your "reputation" and "trustworthiness". (very hard to regain)
It would seem polite to contact the company and apologize for the no-show. It's ok to say that you don't feel that you were fully prepared for the interview and admit that it might have been better to contact them as soon as you decided not to progress further.
Unfortunately, you won't be able to give the interviewers back the time that they wasted waiting for you to turn up.
Very few people are ready for an interview. As with everything, practice makes perfect, and that includes job interviews. Just don't waste their time going to interviews for jobs you never intend to accept. The worst thing that can happen to you is that you get rejected. And rejected you will be, over and over again. This happens to everyone and is something you should consider a part of a learning process. Don't take it personal, but instead learn something from each one.
So to answer your question; Don't focus on one company. Never back out because you don't consider yourself prepared well enough. Even if you screw up the interview you can always apply at a later stage.
You should also apologize to the company you left hanging. Not because you want to save the situation but because it's the right thing to do.