Always try to end your listing when the most people will be logged on. For example if you live in the UK then you should list you item in the evening around 9 o' clock when most people will be logged on for the final vital few minutes of your auction. Of course you can always pay a little extra to have your listing end at a specified time but by listing initially at the time you want it to finish you can avoid these fees. Also if you live in the UK and reckon that your product may have a market in the United States don't forget that they are 5 to 8 hours behind you so you need to take this into account. Best of luck.