Choosing a domain name
Finding a good domain is more art than science. Brevity is useful, but not essential, and sometimes a memorable phrase will beat a one word domain (walkyourdog.com vs dogs.com for a dog walking site). Many of the domains which were thought to be pure gold in the early domain rush like pets.com are now sadly simply a redirect to another domain name, and the truth is what you put at your domain is at least as important as the domain itself. TLDs go through periods of popularity (the rise of .io amongst startups for example, .info was popular but now is seen as pretty much dead), and then fade away, and single generic words are surprisingly pointless impotent - better a short memorable name than one which people will struggle to remember. Your domain name is probably the most important part of your web presence so choose it carefully.
Which top level domain, is .com still king?
When you're choosing a top level domain consider your customer. If they are more traditional or older, a .com is still by far the best choice. If they're a little more adventurous they may be open to some of the new tlds, which are cheaper, and more fun. Eventually .com will lose it's lustre, but for now it still carries with it a certain authority, if only because acquiring a suitable .com domain can be expensive and means you probably have the money to pay for it.
What length is good?
Something which is memorable is often the best choice. Not so long that it is difficult to read out over the phone, and without any tricky spelling or punctuation which will trip people up. Avoid dashes and clever use of subdomains if you can - keep it simple. In general shorter is better, but don't pay a premium just for length, and you can break this rule if you use a sentence for example or some other trick to make your name memorable.
Should I use punctuation or emoji?
The jury is out on emoji, because they are not yet well supported in browsers, but punctuation like hyphens is definitely something to avoid if you can, unless it is an integral part of your branding. It is hard to remember for customers and likely many will find similar sites without the hyphens if that domain is already registered.
Should I use www or not?
Opinions vary on this - we've written a separate article about it here. In the past www was used for websites, and other subdomains might be used for other purposes (for example mail. for a mail server or ftp. for an ftp server), in practice nowadays most websites serve on both www and the bare domain, and www is somewhat redundant.
You should try to choose a name that is unique and memorable, so that people don't mistakenly take you for some other business, or end up visiting the .com when you are .net without realising they're in the wrong place. Try to register the unique name you choose under your chosen identity and the .com if you can. For example daintydomains.com leads to dainty.domains, even though the .com is not the primary domain it should be registered so that someone else can't steal your identity later. This is especially important if choosing a new gtld.
Memorable domain names
Your name should be catchy and memorable, it's important that visitors remember how to find you again, and customers who see the name in an advertisement are able to find you easily. To help with this make sure your name is neither so prosaic that it is instantly forgettable, nor so unusual that it is hard to remember correctly. Stick to one or two modifications to spelling (e.g. googol to google), and try to modify it to make it easier to say, not harder.
Your domain name should be relevant to the subject area, it's not good using dogs.com if your business is a taxi company for cats. So try to choose words which your customers will search for and remember, and which make them identify your brand with the area you work in. Again this rule can be broken if the name is memorable enough.
This is especially important for emails - no-one wants to work with people using fly by night hotmail email addresses to transact, and it's important for your business that the domain you choose works well with your branding in other areas and gives you an identity people can trust. So don't use .horse for your business address, or .com for a joke site, have fun with your domain but if your company is a serious one you will want to choose a name people trust.
Traffic and Spam
Also important for trust is the history of your domain if you're buying one which has been registered before. Be careful if you choose a domain name which has been previously used, that it was not used by a spammer - if it was it will have been penalised in search engines. You can also try to optimise your domain name to the area you are covering, which does help somewhat with seo, but this is not given undue weight so don't worry about it overly - other signals like links from trusted sites are far more important for SEO.
Finally, remember you can break all these rules and still do just fine if your product is good enough. Remember pets.com died and is now an ignominious redirect, while google (not even the correct spelling), is one of the largest tech companies around.