Although I sell many iPods, I've also purchased many in the past as well.  Here's a few tricks to keep in mind if you aren't so experienced at buying electronics on eBay.

Feedback... (of course)

Check to make sure the seller you're dealing with has a 98% or better positive rating with at least a few ratings from BUYERS.  Hopefully there's a few buyer ratings in there, seller ratings don't count much since you are now buying.  If there's not much buyer feedback, consider that when bidding.  Look at the items that were bought, and read some of the feedback comments- you'd be surprised at how accurate they are when determining what to expect from a seller.

Shipping

Be sure to get the total shipping amount figured out before bidding, sellers will often pad shipping prices to offset their fees.  Just consider the shipping amount part of your total purchase amount when comparing items.

Condition

By their very nature, iPods can get pretty scuffed up if they aren't kept in a case.  This varies widely depending on use, so be sure to inspect pictures and descriptions closely.  If a seller doesn't offer pictures of the item you are purchasing (stock photos don't count), consider this as an unknown when bidding.  The good news is that even if an iPod is scratched up, it will usually still perform well.

Along with external condition, consider the remaining battery performance.  All rechargeable iPod batteries will eventually wear out - some faster than others depending on temperatures they've been exposed to.  3rd generation iPods and 1st generation iPod Mini's are notorious for poor batteries so look for a description of current battery performance.  If there isn't one, ask the seller before bidding.  Most other iPod models have reliable batteries so a description of them is not as important, unless you're one of those people who wants to cover all your bases.

Extras

There are a few accessories you will need to use the iPod.  First, you need a way to connect with your computer for music transfer and charging.  Check to see if your computer has either a USB port or a FireWire (sometimes referred to as IEEE-1394) port, or both.  Then, make sure your iPod comes with the right type of cable - or be prepared to buy one separately.  You'll also need headphones, and you may want an external power adapter for charging your iPod away from the computer.  Bid accordingly based on the accessories you need and those that are included.

Thanks for reading my guide - please rate it if you can, and good luck!

Cheers,

Jake