I have found that the best advice to anyone wanting to buy on ebay is to locate the item that you want to buy and also see if there are any duplicate items that may be cheaper or that have a longer period to go till they are sold and put a watch on all items that interest you.
Sometimes we tend to buy on impulse and this gives you a chance to think about what your buying and depending on the end time, gives you a chance to find eather a cheaper item or realise that you didn't realy want it in the first place, and if you start bidding to early you only drive the price up.
All your watch items are there in your ebay, with all the details so you can keep an eye on things.
If you decide that you must have the item, and it's the best deal that you can get, then decide how much you are prepaired to pay and don't forget to add the postage on, because sometimes if you have to pay a lot for postage you can sometimes buy the item cheaper brand new.
Anyway, decide how much you will spend and stick to that amount. Bid on the item in the last 10 minutes, don't wait till the very last minute as sometimes the page might be slow loading and you could miss out. Bid the whole amount that you are prepaired to spend and if your out bid decide if your going to spend more or quit.
Alot of the time if the item is at say $14 and you are prepaired to spend $25 you might be lucky enough to get it, because alot of people just bid in dollar lots.
Hope this guide has been a help to somebody, this is how I do it and it works for me as a buyer.