It depends on what you have to sell.
Generally, if you have something that has been discontinued for a while, you will get a better price.
For example, I have sold several older OS CDs, installers for 98 and Mac OS 8, mostly. These get good $$. Also, I've sold an old serial modem that got a good price.
Generally, if it fits to an old piece of junk that requires very specific stuff, you'll get good $$. Particularly serial peripherals, because they haven't been manufactured in so long (think how long USB has been the standard).
On the other hand, stuff like processors and so forth, don't fetch anything close to market value.
My biggest tip is learn to be patient. It's just about the time you think someone has stiffed you that they come through, and it turns out their cat had leprosy for a week, and they need the money for a vet.
Also, don't even try to sell AS-IS. Nobody cares for it, and they will retract credit payments faster than you blink, even if the item sold AS-IS.
Don't ever send PayPal to anything but the confirmed address. You might as well burn your money, because at least then you won't be assessed fees when the buyer inevitably screws you.
That aside, build a rep. Buy a few items and sell a few cheap.
IMO . . .
I don't think eBay's a good place as a seller. It is a buyers' market.
I've probably made more money buying stuff cheap off eBay than I ever could selling it. Mostly, eBay is the last thing I try before donating to Goodwill.