just common sense, if anything looks suspicious or maybe too good to be true, then it probably is, I also agree with the above poster regarding using an escrow service, also remember to make sure you have all possible details regarding the site and have them verified.
There are many way to prevent scam such as check this person's history. How much reputation do they have? Check the site statistics. Go on to Alexa, what's the ranking? Is the website indexed in Google? Does it have cached pages? Is it indexed in MSN? Are there backlinks? What's the PR?
If I buy a website for 1000+ I want a little bit more information that the itrader and rep before I send money. What prevents that person from keeping my money and not sending a website?
There is no guarantee that you will not get scammed. However, you can always be safe. For websites over $100 use escrow.com. For smal websites here at DP, you can check their iTrader and previous posts to see if they are to trust or not. Usually people with iTrader don't scam. But be aware, there may be fake DP accounts with iTrader. Talk to the seller on PM, MSN, etc. You'll know it when a 15 year old is trying to scam you.
Depends on what you understand by scammed You need to assure that seller has several proofs of revenue and statistcs, check his website on google, his backlinks, his archive, his indexed , etc. etc. for buying a quality website
Nothing that you can do to be safe, yes the Itrader does effect the buying, but yet there is like many chances that they might scam. For big transactions, do it via a verfied account and keep a track of each and every message you have with the person. Charge back if anything happens. Also it depends on what sort of item is on sale and what you are buying. You have to start with something though.