The way that competition is supposed to work between registries, is that lots of companies go to ICANN and say “We think we can reliably manage .com, and we think it would cost us [$5] per domain.” ICANN reviews these bids and awards the .com contract, which lasts for a fixed period of time, to whomever they deem best-suited to the job. In this time, other companies can think of ways to manage .com better/cheaper, and try and win the next contract. This, in theory, would provide an incentive for registries to innovate, a big part of which would be in lowering costs.
Those trading domains for commercial purposes are generally on the prowl for lucrative domain endings. There are essentially two different ways traders go about making money off of domain names. One method entails purchasing already established names for a low price and selling them for a profit later once their value has increased. Another strategy involves buying and registering a domain that is thought to possess a high sales potential. Many domain traders use backorder services. These services automatically register a domain when one becomes available or is deleted (what are known as expired domains).
Many online shops have the number 24 in them, to signify 24 hours a day – you may also be able to integrate numbers into your domain in a meaningful way to make them unique. Be careful though, because many cultures attach a lot of significance to certain numbers. Make sure that your number doesn't represent bad luck or other negative things in the country you're operating in.
For the most part, you can pick whichever TLD you prefer, though a few have restrictions -- you can't buy a .edu domain unless you run an accredited post-secondary school. Many, but not all, country-specific domains (.us, .uk, .jp) are restricted to citizens of the country in question. Unrestricted country domains are often used for "domain hacks," where the extension becomes part of the title, such as YouTube's alternate address, "youtu.be."
A great domain name is a concise, easy to type, and memorable URL that reflects your brand or your website’s subject matter. Avoid using hyphens, strings of numbers, or unnecessary words to make it easy for your visitors to remember and find your website. Remember: A great domain name is one that your visitors can type correctly on their first try.