Haggling on ebay

Anyone have tips for haggling on ebay? Be really nice or a bit rude? Mary Poppins or Gordon Gecko?

I don't know about haggling pre-sale, but when I've been sent something that's defective or otherwise gratuitously not as described but still usable, I've had really good luck getting people to give me a partial refund.  Has happened 3 or 4 times, usually with records that are rated near mint but arrive all scratched up but still playable enough that I'd rather have half my money back and keep it than spending probably half of the refund or more in shipping to send it back..

In general it comes down to research and intelligence. Being able to look at details at the item they are selling and being able to find flaws, scratches, marks, wrong spelling in the seller ad, history of what you are buying having defects, the time that the seller has had the item for, supply vs. demand, geographic location etc... The more science you have to back up your claim, the better. If you don't have the smarts, sometimes just bluffing can get you quite a bit.

I was able to make an over my beloved Roland MT-32 for $50 CAN just because the seller could not find any buyers for $200.

A few tips: Ask the 5 W's: Who, what, when, where and why to the buyer. You can find out a lot about placing a value on the product just by finding information on the seller. How much do you want the product vs. why they are selling it. Also look up the product and see what other users have had problems with technical-wise. If you say "I read up that I have to repair such-and-such on the device after x amount of time has passed and I'll need to spend some money on that aspect." is an example that can bring down the cost dramatically.

Do. Your. Research. if you are serious about getting a good deal.