Domains that are indexed on Google and highly ranked are particularly attractive to traders. Other SEO aspects, such as backlink profiles or the search volume of the keywords in domain names, also play a significant role in appraising value. Design can also positively affect the price of a domain. Short and succinct names that are easy to remember are especially advantageous. Endings are further factors that should be taken into account. Top-level domains (TLDs) such as .com or .org are by far the most sought-after endings.
To find popular phrases I opened up the Google Keyword Planner. This free tool by Google, allows you to find out how often a word or phrase is searched in Google. A phrase like “Yoga Mat’ has on average, about 10K – 100k monthly searches. That’s A LOT. However a more niche phrase like “Good Yoga Mats” only has 100 – 1K monthly searches. These seem similar, but I wanted to focus on the exact popular phrase that people are searching for.

If your domain name is related to a particular niche, then you may find success by advertising in forums that are related to that niche. Simply placing a link in the signature of your posts can tremendously speed up the selling process. While it may be possible to find prospective webmasters on niche-specific forums, it is generally better to advertise on webmaster forums, where there is a high volume of potential customers.
What I like to do is sort by DP which stands for domain pop, and this is basically the number of linking root domains. So, BL is the number of back links. As you know that can be somewhat misleading if they have a lot of site wide links or multiple links from the same domain. I like to sort by domain pop. What that does is it brings up the sites with the most amount of referring domains.
Here's a test I have in process.  I bought an old $5 closeout domain from Godaddy TDname expired auction.  I put a quick minisite up and linked to it with a crazy anchor text phrase.  The domain is ranking for that crazy term now.  It's gone through one pagerank update and I'm waiting for a second to come.  Then I'll redirect the domain to another minisite.  I suspect the second site won't rank for the anhor text, but we'll see.  
Yes, buying existing domain names can be profitable too. Existing domains with a potential for profit can be found using Sedo. Make sure you pick domain names that have good traffic, backlinks and Google PageRank under 17 characters. Also, steer clear of existing domain names containing special characters or numbers because they are not likely to be sold.
If you don’t have a lot of money to invest in employees and you’d rather work on your domain portfolio by yourself, you’d need plenty of free time. Generally, mini sites with 5 to 10 pages of content can be built within 5 days, while authority sites with over 10 pages could take up to two weeks. This amount of time would depend on your writing skills and knowledge of SEO techniques.

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! 
At the end of the day, the owner of this domain name let it expire and didn’t renew it. So while there may be many legit reasons as to why they might’ve done that, one of the not-very-legit reasons could be that the domain is “dead” in some way or another. In other words, it’s no longer useful for the original owner because of a penalty or otherwise. If so, it's unlikely it'll be of any use for you as well.
Also with the domains, a name which can be cheap for one can be worth gold for the other. Permute the letters in your domain name and try contacting and eventually selling out to organizations that run under those names or contain the letters within. Companies would be keenly interested in buying out the domain names that matches the product's name. Hint : Look for companies on LinkedIn
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.