When you have done enough research to decide your business theme, the next step is finding a domain name for your online business website. A domain name is the unique name a website must have in order to be published on the internet.
Business Theme as Domain Name
Ideally the domain name should be identical with your business theme (or name), but that isn't always possible to achieve. If the name of your business/title of your website is "Acoustic Guitar Music", ideally your domain name should be 'acousticguitarmusic.com' or 'acoustic-guitar-music.com'.
It doesn't matter if the domain name is written with or without hyphens; however hyphens normally make a multiple-word name easier to read for humans. Space between words isn't allowed.
You should try to find a good domain name that describes your site and also distinguishes your site from the others in your niche. Finding the best domain name for your website is worth the effort, so take your time to research domain names before deciding.
Domain Name Ideas
When you have come up with a good domain name closely related to your business theme, you'll have to do a domain name check to see if the name is available or if it's taken by someone else. There are still lots of available domain names, although many of the 'best' ones might have been taken, at least in the popular niches.
So finding a domain name that reflects your business perfectly isn't always easy, and some tweaking of the words might be necessary.
If your domain name of choice - let's say 'acoustic-guitar-music.com' - isn't available, try adding a descriptive word in there somewhere. Try to find a combination of words that still contains your business theme, like 'best acoustic guitar music', 'all acoustic guitar music', 'acoustic guitar music central' etc.
If you think "out-of-the-box" and search a bit, you can come up with an even better domain name than your first choice! Finding a domain name is much about digging and searching and tweaking.
Checking Domain Names Availability
There are a lot of services (websites) where you can check available domain names. You will find a lot of them by doing a Google search for "check domain name", or you can use my preferred service to check domain names - NameCheap.com. That's also the place I purchase domain names.
Once there (at NameCheap), type the domain name you'll go for in the white slot to the left, then check the extension you want (usually .com for business sites) and click Search. Now a list of domain names is displayed, with yours on top. The second column (Status) shows which domains are Available, and which are Taken.
If your domain is available you may proceed to buy it by clicking the Add to Cart button. If it's a .com domain it costs around $10 per year (at the time of writing). However, a free domain name is often included when you sign up for web hosting - see How to Host a Website.
Domain names cost anything between $2 and $20 per year depending on the provider and which suffix you choose (.com, .net, .info, .us, .eu etc.).
An alternative service to NameCheap is DomainsBot.com. They also come up with suggestions of other domain names, which can be of some assistance in finding a domain name.
If your 'first choice' domain name is taken, you have to figure out another one. Do some brainstorming and domain name checking - use Google's Keyword Research Tool to get ideas. Don't give up, there are lots of available domain names in any niche, and you will definitely find a good one in the end.
Domain Name Formalities
Domain names can be of any length up to 67 characters (including the suffix). Marketing experts don't agree on whether a long or short domain name is better. My recommendation is a relatively short, easy to remember domain name.
Only letters and digits (numbers), hyphens (-) and underscores (_) are allowed in domain names. Other signs as well as space between words are not allowed. Capital letters are allowed, but are not frequently used.
So you may consider applying hyphens or underscores if your otherwise "perfect" domain name is taken (ex., the domain name of this very website is 'start-online-business-guide.com').
As you probably will experience, finding a domain name for your website can be difficult enough. Be patient and persistent, then your efforts will come out successfully!