I worked in retail recently, specifically watches, so understand the niche/geeky clientele it can bring. I learnt that you have to appreciate those who are truly interested and will invariably just be in to browse and kill time, but at least have a quick chat with them.
Yes, it takes you away from other tasks. Yes, it might not be a sale, but at some point it will be if you do the right thing. Timewasters can be annoying, and I can see that being a big problem in guitar shops, but customers keep the doors open.