Are valuable domain names all taken now? No.
You can still create a domain name that represents the subject of your website, yet is different from existing registered names. e.g. If you are a plumber the domain name plumbers.com.au may be taken, but not smithsvileplumbers.com.au etc.
You need to avoid being similar to existing names if you want your customers to stay with you and not be confused.
Your domain name should be easy to remember, and therefore easy to spell. Although you can register a name up to 67 characters long including the .com part, such names are hard for people to remember and tell others about. The shorter and simpler the name the better.
e.g. generoushostinganddomannameregistrationdeals.com has only 48 characters but we couldn’t hope to spell it from memory, so wouldn’t expect anyone else to.
If a long name is unavoidable, it may be easier to remember and pronounce if it’s hyphenated. However, when people tell others they won’t remember the hyphen. So if you register a hyphenated name, then also register the unhyphenated version.
If the name has keywords it will help in search engine ranking. For example platypushosting.com.au contains the keyword (for us) “hosting”.
If you create a long hyphenated name for the benefit of search engines, you can always create a short version for emails etc. and make it an alias on the same website hosting.
If the name you want is already registered as a .com, don’t take the .net or .org version. People will not think of the other versions — they are more likely to just remember the .com.
If you are starting a new business, it’s probably wise to choose a domain name then a business name to match.
Subdomains are another option. Subdomains are free and do not need to be registered. They just need to be hosted with a domain name.
Your name should be easy to remember and easy to spell if you hope for word of mouth referrals.