This guide is for buyers to tell them when to bid. I am a frequent seller but sometimes buy items maybe a once every few months.
Being a seller, you learn a lot about people bidding. Sellers can see how many people have visited their listing and how many watchers there are which are important to sellers. Watchers are potential buyers I say. If you have 20 watchers, that could be 20 bids.
For example, if I had a 7 day listing, I wouldn't expect a bid until about 3 days left. If the item was popular, I could get plenty of watchers though. I've also noticed that early, first time eBayers bid early a lot for some reason....? If there is a bid with 3 days left, and you really want the item, I suggest that you don't bid until the last day because bidding with lots of interest with lots of time left encourages people to beat you. If I am buying for something, I will wait for the last day and be a watcher. With about a minute to go I would constantly refresh the page for new bids and then strike with 20 seconds to go. If you have fast internet, you can normally expect the bid to be placed with about 7 seconds left, giving you the item. It is very important that you don't bid early if you really want the item because you are sure to be out-bid, therefore raising the price. The method of bidding with 20 seconds left has worked every time for me. Another tip is to know the benchmarks for bids. If the starting price goes up in pounds every bid, and the item was £4, put a bid in for £5.01 so you are winning and the next bidder would have to put £6.01. This makes it harder for the rival bidder because it is shown that you only have £5.00, not £5.01. This is also successful if you are bidding early and also helps to get the item.