Over the last 2 years I've bought and sold a range of goods off E-Bay - from golf equipment and guitars to electrical equipment and silver bullion. Some were bought at auction and some on a 'buy it now' principle. Before I describe my own rules for bidding/purchasing, let me say that I have never had any items delivered to my home in Thailand as I, like many, do not understand the vagaries of the import/export system. Instead, I have them delivered to the UK where I collect them on my biannual trips back and then re-sell. I have a couple of simple rules which I stick to before I buy or sell which may help any newcomer to E-Bay:
I don't buy from any seller with a rating of less than 95% (this is the positive feedback response from purchasers of his/her products and is clearly displayed).
I don't buy any product which displays a generic photo of the product (ie one cut and pasted) rather than actual photographs of the product being sold. (This is particulary important when buying second hand items).
If I'm in any doubt regarding the authenticity of a product, I'll ask the owner for more information regarding where bought/receipts/serial number etc. (An inbuilt question box allows you to do this quite easily). Remember that E-Bay is probably the most used site for the sale of 'copied goods'.
I always pay and receive payment through Paypal. Their charges are a little high but worth it in my opinion for security and safety reasons.
I make payments without delay and ensure that I post items promptly. At the conclusion of our transaction E-Bay asks the other party to rate me as a seller/purchaser and it's important that I maintain my 100% positive feedback record.
I go out of my way to describe the goods I'm selling as accurately as possible, sometimes going a little overboard on the faults. When selling, I use the option which allows me to download multiple pictures into my advert. Whilst this option costs a few pence more, I have found that prospective purchasers are far more confident in bidding when they see that the seller is going out of his way to show that he/she has nothing to hide. When buying, I expect a genuine seller to adopt the same principle.
When buying, be aware that a fair number of non-business sellers to not want the hassle of posting large items. Make sure that they will post to your home country and confirm the cost with them before entering a bid.
When bidding on an auction, I use an electronic bidding system to bid on my behalf 10 seconds before the auction ends. I won't mention the name of the company, as I don't want anyone to think I'm advertising. Let me just say that the results are very impressive.
In conclusion, your first occasion using E-Bay, (especially an auction), can be a little daunting. Just be a bit careful and I'm sure you'll have as much pleasure out of the experience as I have. But beware that it can become a bit addictive.

[i]'The ability to recognise the extent of your knowledge on any particular subject is a condition which, (unfortunately), far too few people are afflicted with'.[/i]