When I walk into a guitar shop where no one knows me (i.e. outside of Iowa City or Newcastle), I will introduce my self to the sales person with words like

"Hi, I have been playing for 20+ years and Im looking for a... or a something like...."

The only problems I usually have is that they don't have what Im looking for.

I also make a point of knowing the going rate for what I want. If they are not willing to at least match the on-line price then I can always walk with my Visa card still in my pocket and fully loaded.