how to put a reserve price on an item

Read up on Reserves here:

http://pages.ebay.co.uk/help/buy/reserve-price.html

Bear in mind that the minimum Reserve price you can put on your listing is £50, and it's a very expensive feature to use. You pay for the feature (£1 plus 3% of your Reserve price) whether your item sells, or not.

It's best to just start your auctions at the minimum price you'd be happy with.

It is also a false economy to list for free at 99p then pay for a BIN. At the first bid the BIN disappears (fee is not refundable) and you could end up selling for 99p.