The relationship between IT managers and vendors has always been fraught with conflict. Each party's divergent interests and motivations make it hard to find common ground. Despite the effort IT vendors and buyers put into patching their seemingly irreconcilable differences, the relationship still doesn't always work out. Sometimes, it's the little things vendors do-the things they're least aware of, such as bickering with their own tech support people during pitches-that make IT leaders lose confidence. Here's a list of common mistakes vendors make when pitching to CIOs.

They're arrogant. A vendor's haughty attitude is the biggest turnoff for Charlene Barnes, the executive VP and CIO of mid-market wealth management firm JBHanauer & Co. She once worked with a telecom provider that thought so highly of itself it couldn't fathom any reason why a customer would not want to do business with it. Particularly troubling was the company's "our way or the highway; we don't need your business" attitude.

Barnes didn't put up with that shtick for long, and she ended her company's relationship with the telecom. "I don't care what kind of monopoly there is in the market, you [as a buyer] have a choice," she says.

They arrive late. Punctuality is Sales 101. It's common courtesy. So when a vendor is late for a meeting with a busy CIO, it's a huge demerit. "We had a meeting scheduled with a vendor, and they were like 25 minutes late," says Joe Miller, senior director of IT at Xoma, a bio-pharmaceutical company based in Berkeley, Calif. What made the delay especially egregious was that it did not just disrupt one person's day; it inconvenienced many Xoma employees. "We had 30 people sitting in the [conference] room waiting for the vendor," Miller recalls.

There's no excuse for being late even if the salesperson is meeting a client in the San Francisco Bay area. You know the traffic is awful, so get on the road early.

They're too aggressive. No one likes a pushy salesperson, whether they're peddling shoes, cars or software. Rey Arellano, CIO of the city of Tacoma, Wash., has had his share of experiences with overly persistent vendors. A consulting company that had been on his tail in previous jobs reconnected with him when he joined city government. Whenever he had a conversation with one of the vendor's reps, he says, the rep would ask, "When can we follow up with you? Is next week OK? If not next week, how about the week after that?" Arellano didn't like the way the vendor constantly tried to pin him down. "Sometimes they just see us as a sale," he says.