I hate it when they ring up and first thing they say is 'whats your lowest price'.
Had loads with my bike recently, if they had asked me the right questions about the bike, asked for high res photos and lived far away i'd be happy to arrange a price on the phone (i've done this myself as a buyer and seller).
But when they live 30 minutes away I want them to see it and make me an offer in front of me. If I was 30 minutes away and was interested i'd go and have a look before talking money.
Oh and people ringing and saying I can get one that 2 years newer for only £500 more :S Well go buy that one then lol