How long has the agent been in the business?  Everybody's got to start somewhere but do you want him or her to start with your business.  I remember making lots of mistakes when I was brand new in the business.  

Is the broker solely a commercial specialist? Don’t pick a residential broker to negotiate your Lease. This will be a huge mistake!  Seems like a no brainer but I've seen it done lots of times.  

How much of their business is Landlord oriented versus Tenant oriented.  How many listed properties do they represent and where are they?