First you'll need to show them a new point of view. The point of view that says that 'just looking' is not the end of a conversation, it's the opportunity to start one. Always response in a positive manner such as "Great!". Always offer your name to start that personal connection, "Great! My name is Scott, it's a pleasure to meet you. Thank you for coming in.". Than always offer to help and/or to add some beneficial information for the customer,