If you are planning to buy domain names, there are certain things you should keep in mind.

1. Make it clear who is responsible for purchasing the domain name:

If it's for a client, we always make the client pay for the domain. We usually ask them to create an account with a domain registrar and add their credit card. Then we ask them to let us have the username and password so we can log in and set things up. In this way, it is entirely their property, and it is entirely their responsibility.

2. Make sure the correct person is the legally registered person:

If it's for a client, this should be the legal registrant of the domain name registrar. If you purchased the domain using your account, this should be fine. But don't make the mistake of having your name and details as the legal owner. It can be a nightmare to change later.

3. Choose something short, easy to remember, and without hyphens:

Google has historically viewed hyphenated domain names, like my-fabulous-web.com, as being a bit of a spammer. They are also more difficult to explain to people over the phone or in person.

4. Don't worry about keywords:

The days of Google ranking domain name registration based on stuffing them with search-engine-friendly keywords are over. It's much better to have a domain name that reflects your client's brand, which is often related to the company name, not a list of the products they sell.

5. It is okay to buy multiple versions of the domain name:

For example, the .com, the .net, the .org, etc. But only do it if you want to prevent someone else from buying them, and therefore to protect your brand.

By the way, don't put a live website on each of them, thinking that it will somehow increase visibility for search engines or something. At best, Google will just pick one of them to rank and ignore the rest. 

It looks like spam! If you buy multiple versions of the domain name, my advice would be to set up a permanent redirect from everyone else to the main live one. Most domain registrars have that utility in their control panels. It could be called a 301 redirect. A 301 redirect it's just code for the permanent redirect.

6. Make sure you set your domain to automatically renew:

It's usually set to auto-renew by default, but be sure to check that it's set correctly. Because if not, you or your client will not be able to complain if the domain name accidentally goes down. And if the domain is under your client's registrar account, then it's their responsibility anyway.