I'm assuming you want to host multiple sites on a single IP address and that you're using apache. If so, then essentially, the following lines of code in my httpd.conf do the job for me:
CustomLog /usr/local/apache/logs/site1.company.com.access combined
CustomLog /usr/local/apache/logs/site2.company.com.access combined
Where a.b.c.d is your server's IP address. Repeat VirtualHost declarations as you need them. The CustomLog declaration isn't vital, but it helps me to keep my sites' logs separately from one another.
You can find more documentation on apache at http://httpd.apache.org/docs/; click on the version of your apache server, then enter (eg) NameVirtualHost in the search box (though the doco for that can also be found directly at http://httpd.apache.org/docs/current/mod/core.html#namevirtualhost - it's not a feature that changes much between versions).