Buying on eBay requires knowledge and patience. If you don't know the product you're bidding on and what it's worth, you can get ripped off. There are many compulsive bidders, when they bid an item above what you want to pay for it, it's time to just let it go.

I only bid by what's called sniping. I wait until the last 10 seconds before bidding. I prefer to do it in person, but if the auction closes at an inconvenient time I use an online bidding tool. Don't always win the item, but I never bid more than I want to pay and I never get sucked into a bidding war.