hehe, i know the feeling of being ignored.  my solution is to be a total ass.  whenever i go to a dealership on a mission, i always make sure my car is spotless, then i usually park as close as i can, sometimes leaving the keys in the car, or maybe even double parking the front two spots (rarely on both)  and then i walk in like i own the place.   
i know what you're thinking, thats kind of stupid.  yeah, and thats the case when i'm daring and have a clean car, if not i just walk in and ask a vague question about the car, then totally own the sales rep by going on and on about specifics of which he's never heard before.
own3d