This is a full list of all the entries you can put in your command line when you launch your Half Life Dedicated Server:
(the command line is the thing that looks like "./hlds_run -game czero +maxplayers 16 +map de_dust_cz" or whatever)
For example, -game czero. Put this command first in your command line. For a full list of games, check out this thread
Launches the game in console mode. (That's for Windows only - in Linux you're already running it in a console.)
Disables VAC security.
Limits the number of map and game entities. The default is 900, and I wouldn't really even add this command unless you know what you're doing.
+<console variable> <argument>
For example, +sv_maxrate 10000. Or even +hostname "Server Name" if you want to set the hostname through your command line.
Set the IP address the server uses. Use this if you happen to have multiple network cards.
This is the map the server will launch on.
The number of slots the server has.
The port the server is on. You must specify this if you're running multiple servers off one machine. The default is 27015, and you can't have multiple servers on the same port, so you'll have to specify something else for other servers. Make sure that you're picking a port that you've forwarded in your router.
For linux servers.
I got this information from this thread, which has a lot of other useful information.