Don't use punctuation in domain names

Your domain name is an important part of your brand. You need the brand to be memorable, easy to pronounce, and easy to type - using punctation makes all of those more difficult.

One of the most infamous uses of punctuation in a domain name is in the domain for delicious which used the .us tld to construct the word - quick, without looking it up, type out that domain name and see if you get it right. You probably got it wrong, because after you remember the word, you have to remember exactly where they put the punctuation to make it up. The right answer is del.icio.us which doesn't exactly roll of the tongue. Of course if you make puncutation a core part of your brand like this, you might be able to get away with it, but think carefully before you try.

Now that many other top level domains are available, you don't have to settle for a variant on the name you want under .com, you can also explore other options - see if there is a relevant tld which you can use for your domain idea instead, or think of a short phrase which doesn't have a hyphen. Anything to avoid punctuation.