In the race for Fairfax County School Board, voter concerns and candidate promises vary from place to place. But there is a consensus countywide that one of the most important issues is the selection of a successor to Superintendent Jack D. Dale after he retires in 2013. Each of the 15 candidates for nine district seats in the Nov. 8 election says the next schools chief must be an excellent listener and communicator. Some say he or she must have a record of closing achievement gaps in diverse communities. Others want someone who can foster a culture in which teachers aren’t afraid to challenge policies.