Selling on Ebay: Doc, I just noticed Sushi's post re ebay and I see he wants selling tips, not buying tips.
Here's what I found -
You can liquidate your own leftover hobby stuff but don't expect to make a profit. As I noted above, a unique photo taken in your home will help distinguish that your stuff is in better condition than the Power Sellers' customer return or pawnshop stuff.
To make any money on ebay you need to find a product with a good markup, ideally $50 or more. And you should sell identical items. If you are offering all unique stuff then the effort to photograph each one, do the research to find a good description and a good starting price, and then answer questions will be overwhelming. It's easy to fall into the trap of churning a lot of work that ends up earning $5/ hour. By selling identical items, you only do the marketing research once.
Look at the range of prices for completed auctions on similar items, and set your starting price to at least the 70th percentile or higher. Many times there will only be one bidder and you never want to sell for a $1 starting bid. I used a buy-it-now price around 80th percentile or even higher and was surprised that about half of my tape drives sold that way, usually higher than what people bid the other ones up to. For commercial stuff there seem to be buyers who only look at the BIN and buy immediately with cost a secondary consideration. And a high starting price avoids questions from people who don't know what the item is. You want to sell to someone who can put it in service without your assistance, and if they should make a warranty claim, you respect they know what they are talking about.
There's a lot more, but this shows it is harder to make money on ebay than it appears. Most who try selling on ebay quit when they realize there isn't the opportunity for a good markup because they can't find a source for a unique and profitable product.
Making a dollar or two on a huge volume is a specialty that few people can master. That is probably the hardest way to do ebay, I don't recommend it.
You need to find a reliable source for merchandise. Here is what worked for me, maybe you can find something comparable: A local shop specializes in bidding surplus electronics auctions, including government and high-tech. - Apple, Intel, HP, Chevron Labs (petrochemical) and many Silicon Valley upgrades or (in 2001) company failures. The Y2K fear caused firms to dump perfectly good stuff and I specialized in finding the tape backup drives in his pallets of widely varied stuff. My cost was $50 each, then typical auction price $175 for one model and $275 for another.
The place where you make money is by finding stuff well below what it will sell for on ebay. You can control cost, but you can't control sale price when others are selling similar items.
Anybody want a 35-70gb DLT drive? I'm down to my last two!
[this should have been a link, not an included photo. I don't see how to do that.]