I got my initial phone screening because I knew a current employee. That was a huge help, especially because I got to check out the office before I started the interview process. It's a very cool office with multiple floors of young sales people working there asses off (that's a good thing). They also had a cool "hang out" floor with pingpong tables and beers on tap.
That aside, I did enjoy the interview process. I started out with a initial phone screening that was really straight forward. I actually think I performed terribly (stumbled a lot and was not very confident). But really what they were looking for is someone who really wants to get into sales and is willing and ready for a lot of phone interaction. I think they were just checking to make sure I wasn't crazy before they brought me in.
They ended up giving me an in-house interview a week or two after the phone screen. I was interviewed by three sales managers, all of whom were very nice and easy to talk to.
1) The first asked me general sales interview questions (why sales, why Yelp, etc). Then asked to do a mock cold call to a pizza place. What they are looking for here is for you to first and foremost be friendly and ask them a bunch of questions - then get to the point and set up a call for a future date. I beat around the bush and asked and went into and in depth explanation of Yelp (which is not necessary) and wasn't direct about setting up the next call. Get to the point.
2)The second asked me to do a mock 2nd call where you need to figure out how they currently advertise, what their main problems are, then close. So basically I picked up where I left off with the pizza place. I think I did well here. Ask a ton of questions. You really need to figure out what their pain points are about advertising and direct your pitch towards those problems. Smile the whole time and don't talk too much. Really get a good understanding of the customer then close based on their answers. For this you really have to know the product you're selling well. There are plenty of resources for this on their website and their blog.
3)The last asked me which of the first two calls did I perform worse on. Then I got to redo that. So I chose the first call and I really killed it.
At the end of each interview be sure ask how you did. You not only will need this information to help in the next part of the interview but you'll need that feedback for any other interview you may have. Bring a pen and a notepad and write it down. You'll get some really good feedback.
I got a call a week or so later telling me they were doing a background check (that's a good sign). Then 2 weeks after that I got an offer.