In order to maintain ownership of a domain, you must renew it yearly. If you don’t, it “expires”. An expired domain goes through several stages before being released again for general registration. The process differs slightly from one registrar to another but it’s more or less the same. GoDaddy explains what happens to domains that expire with them here.
Hi Kulwant, these are great tips as usual. I particularly like the way to tell us to check the google pagerank in case the domain has been banned – that could lower the usefulness of the domain quite a bit. One thing though, don’t you think that buying domains is sometimes immoral? Like sometimes you accidentally buy a domain of somebody elses website who forgot to renew.

I did this last month, snagged a great domain that no one else found and got it for $69 because I waited until the last moment to place my pre-bid. Flipped it within a week for a little over $1,000. And probably could have gotten more if I sat back and waited 6-12 months, but a bird in the hand… (plus I like to keep turning over inventory and maintaining cash flow).
Granted, it is not bad information, however, if EVERYONE rushes to namejet and signs up, the only people that really benefit are namejet 😉 The increase in competition means there are more bidders in the pool which will likely increase bid amounts (because the newcomers will not be able to ascertain a “true value” as much as a “pro” flipper would). The result is a lower profit margin as the method becomes saturated.
Just because someone spent five or six figure amount on a domain name doesn’t automatically imply that he/she’ll spend the same or at least a few thousand dollars on a similar name too. Basing your domain flipping strategy entirely on what others have just bought may not be as useful as you may think. Every domain name has a story behind it and its purchase/sale is usually as unique as that story.
Buying a trademarked domain name could get you into a lot of hot water. Best case scenario is for the trademark holder to force you into handing the domain over and call it a day. Worst case scenario is you get into a legal battle and end up spending an arm and a leg. This is why it might be a good idea to use the United States Patent and Trademark Office’s (USPTO) website to check for trademarks if you’re unsure about a domain name.
The domain name industry is quite similar to the real estate industry in a lot of aspects. There are end users, brokers, consultants and domain flippers or “domainers”. Domain flipping works similarly to buying a house, renovating it (or even sometimes just sitting on it) and then selling it again at a higher price point. The gist of it is: you’re purchasing a domain name and betting it’s worth (or will be worth) more than you paid for it. If you’re right, you get a nice paycheck and move on. Those who make a living out of this just rinse, repeat, and scale.