htaccess codes

Does anyone know what htaccess codes will direct visitors to a list of different names for your blog?

ie:

“yoursite.com”
“yoursite.com/index.php”

And a related question. I have a second blog that runs on a sub-domain. I have not been able to get it to follow the correct URL format for a sub-domain.

At present the URL is “firstsite.com/secondsite.com/index.php”

What should the htaccess be to use the correct format?

ie “secondsite/firstsite.com/index.php/”

Thanks