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.
Selling on auction sites is another great way to find buyers. Ebay.com is perhaps, the most popular place to sell domain names. Afternic.com is another site that allows sellers to find good buyers. If you have premium domain names, become a member at GreatDomains.com and list your domain name there. The site is a reputed marketplace and brokers deal with thousands of dollars trading domain names. You can also sell domain names through Sedo.com, a site which has its own selling program. Sedo.com has the largest marketplace in the world, and boasts of having a list of the most expensive domain names in the market. It also has a safe and secure escrow service for domain name buyers and sellers.

However, I'd argue that most people in the business really struggle as they don't understand what makes a good domain name and what's a bad domain name. While I do not work in this field full-time, I can say that I can make a living of it, but it's probably because I don't ask for absurd prices (e.g. randomword247.com domain name for $8000 is just unrealistic and won't happen) and therefore can sell domains easier. 

Internet users, who try to find expired domains and re-register them, will soon discover that this plan cannot be manually accomplished. Professional domain traders are familiar with the registry deletion process and rely on sophisticated algorithms that indicate when a domain is about to become available. Deletion lists are the result of this research. You can find many datasets online with domains that have already become available or will soon be. You often have to pay to be able to see this information.

Domain names expire when someone decides to stop renewing it. They may not be available to register immediately. We update the search index every night, so some names may already be renewed or re-registered. Some may become available in a few days. Some registrars, like GoDaddy, will let you buy a name that one of their own customers expire immediately. When you find a name you like, just click on it to try backordering the name!
What type of business are you considering of building something on using the domain name?Is it something you believe in and willing to put your all, how much can the monetize with the website, etc..Ask yourself much questions before proceeding to finally selling it.Also, it doesn’t matter if a different company is using a different extension.It means you have upper hand to get their traffic if you build something using the .com.Good luck
Here’s what you DON’T want to do: Target prospective buyers based on their perceived economic status, without any insight into the industry you’re targeting. “Lawyers seem to do well,” you think, “maybe I should start selling names to them.” So you rush out and buy a bunch of domain names you think would appeal to the law firms you’ve identified as potential buyers. Without knowledge of the space, you may not know that the American Bar Association and other industry-specific organizations set rules that govern some aspects of legal advertising. You’re not going to strike gold selling names your target buyers can’t use.
Domain flipping is the art of buying a good domain name at a wholesale price and successfully selling it at a resale price and making a profit. I’ve been helping clients flip domain names for over 10 years. The skills needed to be successful is some working capital, knowledge of domain valuations and a good information flow from a trustworthy domain broker who knows the landscape and can help source you the best deals.
Now it’s time to transfer the domain name. Every site has its own process. Generally, the domain-selling sites require sellers to submit the authorisation code, which will initiate the transfer process. Once the transfer is completed, the seller can transfer funds from the escrow account to his personal account. Do check for the minimum number of days the amount must stay in the escrow account before the transaction can be completed.
I OWNED DOMPERIGNON.ORG, incredible, but true.  Lost it, back in the days when internet in India was not a readily accessible utility. And I was a casual domainer.  You had to go to a cybercafe. Did that late in the day, towards the expiry of the domain. No chance of renewal. The domain is now with the owners of Dom Perignon and is redirected to domperignon.com! 
There comes a time in the life of every domain when its ownership must transfer hands. The reasons for selling a domain can vary greatly; maybe the company is no longer being in business, or the domain was bought in bulk and never used. If you're looking to offload your extra domains to make some spare cash, or if you're sitting on a premium domain name worth a goldmine, see Step 1 below to learn how to sell it.

If you buy keyword specific domains, you're really buying the type in traffic.  I use the URL builder and redirect through that URL so you can see how much traffic your getting from the keyword domain.  There seems to be no rythme or reason to what keyword domains deliver traffic and what don't.  By tracking traffic with the Google URL builder you get a feel for what names are giving you traffic and which are not. ie. the plural, the singular, two words, three words, the possessive, etc.
There are several types of domain names to avoid. One is intentional misspellings, as these make it less likely someone will search for them. You also want to avoid names with extra symbols like hyphens, or with added prefixes and suffixes like "e" or "my." Outside of a few notable exceptions with very strong brands (like eBay), those additions can only hurt the value.[3]

There is a misconception that good ‘.COM’ domain names are hard to find and so they are more expensive to buy. But once again, this statement holds no water. You can easily check out the ‘.COM’ domain names that are on sale at highly affordable prices. However, the only downside to flipping ‘.COM’ domain names is that you will have to discover them at different places like Flippa.com or private seller portfolios.

Ur article is good but the problem is Flippas RESERVE PRICE and STart PRice are Ridiculous conflicting features.. which means sellers have no freedom to choose a good price.. But flippa gets its $10 even if seller makes $5. How shameless is this platform. Also, flippa is using a thirdparty brandable API for escrow, which allows them to charge ANY AMOUNT for escrow fee, and they are charing $25 in the name of third party. Serously flippa is a bunch of crooks
Surely if you purchase a domain (domain1.com) and redirect it to your existing domain (domain2.com) you expect to loose all ranking for domain1.com. If 301's are used then the objective is simply to pass on authority, not dominate the search results with 2 domains. If you want to keep domain2.com in the index then you would take Rebecca's option 2 or 3.

I've seen some people comment about losing the link value of domains that have expired and picked up, but what about non-expired domains?  Let's say a competitor is going out of business and they still have a year or two left, and we buy their domain and site.  Is there a risk changing registrant info and registrars, even if I keep their site up and mostly the same as before?  I was under the impression that I'd want to keep it under their name so as not to hit the uber-reset button on the domain's inbound link value.
The truth is that you require at least one year’s time to get around only the basics of the domain flipping business, leave alone making huge money from it. During this time, you’ll make several mistakes, buy useless domain names, lose out prospective deals and much more. Domain flipping is far from any get rich quick method. If overnight results are what you’re after, domain investing may not be your piece of cake. This business involves a real and steep learning curve which many people find difficult to climb.

Contains, Starts, Ends You can use the search bar to search for domains that contain particular keywords you are seeking, e.g. a search for "car" will yield results for all expired domain names that contain the term "car". You can also use the search tool to find domains that begin, or end with the search term too, with the drop down box next to the search form.
Contact Potential Buying Companies: With my domain IHateCold(.com) I will email the marketing teams of some of the large winter clothing companies and let them know of the available domain to buy and a few potential slogans they could use with the domain name. This is a very “I’m here to help you” scenario that I’m curious to see how it plays out. They’ll have to learn about the domain name for sale somehow, right?
Many non-savvy internet users may not even be aware of the existence of other extensions. That said, because there are many new extensions popping up every now and then, you can often find amazing one word and 3-letter domain names with these new extensions that are otherwise almost impossible to find unregistered in the .com world. Additionally, these new extensions are becoming more and more familiar to users every day, hence it's almost certain that their value will continue to increase as time passes and wider adoption manifests.