My tips for getting the best prices possible:
Clear photographs, nicely presented (good background and lighting). I crop my photos and reduce the file size so that the auctions don't take too long to load on dial up connections. However, this is only really an issue as I often add 5+ pics to to an auction.
I use Auctiva - then you can add lots of photos for no extra charge. You can also schedule auctions for free.
I list all week, and schedule auctions to start on a Thursday for 10 days. Then you get two weekends of potential viewers.
Add as much detail as possible about condition and flaws. I also say that if the buyer finds a mark or something that I haven't mentioned, then I will happily refund once the item has been returned.
Add that you are a pet/smoke free household if you are, and that all items will be freshly washed prior to sending.
Add a link to 'sellers other items' people often bid on a few things.
Offer collection in person as an option (don't accept Paypal for this though as it leaves you open to scams), and a reduction in P&P for multiple wins. You save 20p on all subsequent items if winning bidders pay in one transaction, so it's worth trying to get them to bid on a few things.
Make sure your P&P is reasonable. I would say an absolute max of £1 above the actual cost of stamps. Less if you are not using professional mailing bags (I buy these from Ebay), and posting promptly. I say that I will post the same day if payment is made before 12pm, so often make a few trips to the PO per lot of auctions ending. Hence the P&P charge is more than the cost of the stamps and packaging only.
22 feedback is OK. Not ideal that it is only for buying, but most people probably don't look that deeply. Paypal makes people feel a bit safer IMO.
Have probably missed lots, so hopefully others will come along and add some more ideas for you.