I like straightforward. When I really want a bike, I look it over closely and contact the seller directly. I like having my bargaining chips ready if I think the initial price is high. If high, I bring out the bargaining chips and try to negotiate a lower one. If that works, great. If it's still too high in the end, I pass. If I like the initial price and what I see, I just buy it. It isn't innovative, but it works often enough. It's tempting to throw in editorializing comments in negotiating sometimes, but generally to be avoided. Actually, the "I don't know, what do you think it's worth" reply is a good opportunity to bring out some of your better bargaining points as reasons for your offer.