Items to do 24 hr auction?

I never recommend a 24 hour auction. Everything I do now is BIN, but I used to sell via auctions.

For quick auctions (Either one day or three day), you'll want desirable components. This means working items that everyone needs. Computer RAM is a good example here. If you have a name brand of RAM, and it's a currently used part (Crucial DDR3, for example), there will be enough people looking that a 3 day auction will do very well. A 1 day auction can work out for these items sometimes, but I just don't like to take the risk on it. For the above example, you'd probably be fine.

For scrap lots, a longer auction is better.

For uncommon items that aren't in high demand, a BIN is the way to go. It will take longer to find "the right buyer", so you don't want a fixed ending time.