I'll share something that works well for me...if it's something that you just don't HAVE to have right now, like that briefcase probably was, I'd wait to make first contact...wait two, three weeks...even if the ad gets pulled, I'd wait...after that time, either it's been sold, OR...the guy's figured out that he's asked too much, OR...nobody's responded because his asking price is way too high...thataway, you're gonna meet with a softened seller...he just ain't gonna be as frisky as he once was...
Take only enough cash with you to meet the highest amount you'd be willing to pay before you walk away...not ten bucks more...Look at the bike, ride it, if there are owies or blemishes, say nothing, but simply rub your hand over them, or eyeball them very closely. Don't believe the seller when he says he's entertaining other offers...if he was, he'd of sold it by then. Don't believe him when he says he has others coming to look at it...by that time, nobody cares any more. When you're done lookin' and jawin', whip out your roll and offer cash...for whatever amount you figure is fair... negotiate up to the amount of cash you've got...if you don't close the deal, walk away. Don't make a standing offer. Just walk away. Tell the seller you're gonna look at a couple more that afternoon. Lie. It's ok.
Follow up a week or two later. Same offer...maybe even less. Do this until you figure it ain't ever gonna work.
You'd be surprised just how well this technique works. It requires discipline and patience.