I've purchased several things off of E-bay. Here's my tips:
1. Read the feedback. Only bid on items from sellers with plenty of positive feedback and little or no negative feedback (take time to read the negative feedback, sometimes the seller is able to explain what happened and how they corrected it).
2. Read the description. Then, read the description again. Ask any questions you have of the seller BEFORE you bid. Read the payment instructions. Can you abide by the payment instructions? Some sellers want money orders (another expense for you), many won't take personal checks, some want to be paid via Paypal, etc. Be sure you are ok with how they want to be paid. This is where a lot of transactions break down.
3. Decide on the maximum you are willing to pay and do NOT go above that. Some folks get caught up in the excitement of bidding and end up paying too much. You don't want buyers remorse! Make sure to factor in the cost of shipping. Some sellers ask too much for shipping, so I always factor that into my bid (and bid less).
4. If you win, be ready to pay right away. Sellers get discouraged with buyers who win and take weeks to pay. That's not fair. I usually send payment or use Paypal the same day the auction closes.
I've heard horror stories but all of my transactions have gone smoothly. Sometimes the shipment seems a little slow so communication is very important. Some sellers ship once a week so if you win and pay on Monday and they don't ship until Friday, it can seem like a LONG time if you don't already know their shipment schedule.
Good luck,
Peggy