You're there on time, the job description is a perfect match and one look at the office tells you this is the job for you. So what could go wrong?

Plenty.

Everyone makes mistakes. But according to those who do the interviewing, job seekers for tech positions are prone to a number of common interview blunders. To avoid them, you've got to know what they are. Here are 10 of the most common.

Appearance

Techies sometimes dress "from the waist up," says Harvey Bass. They've got "wrinkled khakis and rubber-soled shoes" -- not exactly the image they should be projecting, he says.

Says Liz Ryan, a human resources consultant, "The days when you would not be considered because you [were] dressed too conservatively are over."

Arrogance

Too many techies come across as arrogant in interviews, says Sean Chou, "A lot of techies are very talented, but what comes out is arrogance," he says.

Confidence is desirable, not arrogance. Arrogance suggests "they can't be a team player," Chou notes.

Overemphasizing Skills

Certifications and other credentials matter, as does your technical know-how, but remember: You're there to serve an organization's needs, not to focus on J2EE or Cisco just for the sake of the technology itself. You want to come across as more than an amalgam of your skills.

"Sometimes they just overemphasize the skills," says Chris Little, "They don't understand why that's not a home run. They get frustrated, and it shows."

Not Communicating

Interviewers often favor open-ended questions, but techies sometimes respond with too-brief answers, failing to elaborate or convey their communication skills.

"You should think of each question as an opening to a conversation," says Ryan. A simple "yes," she says, isn't an appropriate answer to the question, "Have you worked with C++?" Candidates need to see questions as an opportunity to discuss the value they will bring to a company.

Or, as Chou notes, "People who are unwilling to communicate will have a hard time working in a team environment."

Unprepared

"With all the information available, there is no excuse for someone not being prepared for an interview," says Leslie Norko, deputy program manager of engineering at Computer Sciences Corp. and a mentor for Women in Technology, a nonprofit devoted to networking and professional development.

Preparation, Norko says, doesn't just mean passing knowledge about a company, but rather in-depth research about the firm and its industry.

Lack of Interest

Candidates sometimes display a lack of interest by not asking about the company's industry, competitors or "the larger business problems" facing the firm, says Ryan.

This comes through, quite often, when candidates are asked if they have any questions. Never say no. "It communicates that they're not interested, or they're not prepared," says Norko.

Too Eager for Perks

Questions about parking spaces, sick days, free soft drinks, and other benefits and perks should be reserved for a human resources rep, preferably after a job offer. "Stay away from what's-in-it-for-me questions," Bass says.

Too Casual

Interviews can be formal affairs. The interviewer, not the candidate, should set the tone. "Techies tend to be a little casual in the interview," Bass says. This may come across as a lack of seriousness, or even a lack of interest in the job.

Too Negative

Some techies smarting from tough times -- failed startups, corporate layoffs and the like -- may mistake an interviewer's friendly demeanor as an invitation to confide. Ryan says this focus on "the highest highs to the lowest lows" isn't appropriate during an interview. "Candidates use interviews as therapy sessions and don't even know it," she says.

Failure to Close

Techies often fail to close the interview, says Bass. Rather than emphasizing how much they would love to join the company or asking what the next step in the process will be, techies may let the interview "fade out," Bass says. "They're not closing," he says. "They're not selling themselves."