First, never go with a free domain such as greatcasinos.lycos.com - a real domain can cost <$10 so be proffessional.
Search engines (particularly google) prefer hyphenated domains because they can 'see' the words, so it's best to have great-casinos.com as your site but also have greatcasinos.com redirecting to the site because this is better for humans.
If you're targeting a particular country then national domains are fine, otherwise always go for .com if possible. Only go for other TLD if you can get a really good one (eg. poker.cd which is mine
)
Make sure your link exchanges use the text you want eg.
Code:
<a href="http://www.greatcasinos.com">Great Casinos</a>
If you do this, then the value of a hyphenated domain for SEs is greatly reduced.