Just because a domain has expired, doesn’t mean it has to be kicked to the curb immediately. It is worth considering turning the internet address into a parked domain for a certain period of time in order to generate advertising revenue. This allows domain owners to bide their time and come up with a new web project for the domain or to find a suitable buyer.
Even when you register and pay for your domain name, you won't necessarily be able to use the name for several hours or even a few days. The domain must propagate, meaning that the official domain name registry must be updated with your website's Domain Name System information. That's something that occurs on the backend without any need of input from you.

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.

Even if the term isn’t trademarked, don’t buy domains that are just a variation of another domain name. This means avoiding plurals if the singular is taken (mediatemple.net vs. mediatemples.net), hyphenating a phrase (media-temple.net), or adding “my” or some other preposition (mymediatemple.net). Alternately, you might consider buying these variations yourself and set them up so that if someone types one of the variations, they are redirected to your main site.
You should also avoid words that have more than one spelling if your visitors are likely to be confused and mistype the name. Alternately, you can buy both versions of the name and direct visitors from the one you like less to the preferred name. While you do want a short name (see below), don’t go for something so cryptic that people have a hard time remembering it. Word of mouth is a powerful marketing tool and you want to make it easy for people to tell their friends about your site.
Domains are nonmaterial goods. When sold, the only transaction taking place is transfer of domain rights from one user to another. Barring any form of copyright or trademark violation, virtually any domain name can be bought or sold. Generic domain names, such as car.com or computer.com, are not legally protected and can therefore theoretically be reserved by anyone.
Domain names can be used in a number of ways. Direct visitors to your website’s home page or use complementary domains to send them to specific areas of your website ( e.g. yourcompany.jobs for a careers page). Or, forward a custom domain to an existing social media account, like your Twitter profile or Periscope channel. With a domain name you can even set up custom email addresses like yourname@yoursite.social, which can be used to conduct business or communicate with your followers. More.