An amusing filter is the following. Give them a list of buzzwords for different technologies, and ask which they have worked with. Make a couple of them fake made-up technologies. Anyone who claims to have worked with those is a no hire. (Someone actually made up a networking technology, wrote up a good web page describing it, and then used it in phone screens. Any candidate who read back his fake description when asked about the technology was a no hire. I forget the name of the technology.)
More seriously, the biggest things you want to look for are signs of honesty, ability to learn, and how well they will fit in. If they say that they know X really well, and can't answer questions on it, they are not a hire.
More specifically if you're looking for a specific skill set, then try to have an interview process that reflects that.
For instance at one place I used to work we would give people the description of a real but simple application (generate a bunch of reports for use in playing fantasy baseball). We'd ask the person to design a database schema for this. Then we'd ask questions about how their schema would handle various issues. Then we'd ask them to write some specific queries against their schema. This process closely reflected how our CRUD application actually was designed, and so was a good filter for the exact skill set we wanted.
Similarly when we wanted to hire a front end HTML person, we had a graphic artist layout a realistic page, and then cut graphics. All of the candidates were given the image and the graphics, and were asked to write this in HTML in their own time. They were judged by how well their HTML page reproduced the image given, how clean the HTML was, and whether it worked in different browsers. When they came in we asked a couple of questions about the HTML (basically to verify that they actually wrote it) and checked personal fit. That was in fact the workflow that they were going to face in practice, and it proved to be an excellent filter.
So look at what you're hiring for, figure out the skills people use in daily life, and then design a realistic interview that actually tests that. It won't be perfect, but it will be a lot better than most organizations' craptastic interview processes.