Some things I have learned from selling collectables on eBay (I have over 1100 feedback and a Power Seller):
1) If you want to get the most out of a collection, take the time to list figures individually rather than a whole lot. Some exceptions might be for a Transformer combiner team or a lot of low value items. However, most eBay shoppers find your auction by typing in a few key words. Very few browse the category past the first few pages, so unless your auction is ending within the next few hours you will mostly be getting bids by people who have searched in a term that came up in your title. Chances are that when you list a lot of figures in one auction, you cannot put the name of each piece in the title.
2) Always provide a picture and a detailed, accurate description. Use the gallery option. Take multiple close up photos on valuable items. A fuzzy photo taken at a distance is worthless and frustrating. Use sights like Auctiva that will host multiple hi-res photos at no additional eBay charge.
3) Keep shipping charges realistic. Higher than expected shipping prices drive away bidders.
4) If there is an absolute minimum price you want to get, just start the auction at that price. Don't start the bidding low with a reserve. Most ebay buyers dislike reserve price auctions.
5) Avoid listing Buy-it-nows unless you need the money fast or have setup an eBay store. Start the auction at what you would have set the Buy-it-now price. Sometimes you get surprised and the item will get bid up higher than you anticipated.
6) Always be honest in your descriptions. If a part is broken, worn, or stickers are missing, state it up front. Satisfied buyers become repeat buyers.
eBay buying and selling can be hit or miss. I have had to undersell items as well as sold items for a helluva lot more than I anticpated. You win some and you lose some. Buying goes that way too. I remember scoring a reissue Ultra Magnus, reissue Megatron, and reissue Prime (TRU) for about $90 including shipping. Unfortunately, a month ago I went bid crazy on a mint G1 Snarl (I had been looking for weeks and needed him to complet my Dinobots). I foolishly eneded up paying $150 shiped to get him, only to find one pop up in C9 condition for half the price on
http://www.transformerland.com a few days later.