To access the server add this line to your server.cfg: rcon_password "yourpassword". Once you're in the game, pull down the console and type rcon_password "yourpassword". That authenticates your computer to the server so you can use it to use the remote control commands. You must preceed them with "rcon". So here it is, step by step, if you want to change the gravity, fraglimit, and timelimit.
In your server.cfg file is "rcon_password" "awp"
1. Toggle console
2. Type rcon_password "awp"
3. Type rcon "sv_gravity" "200"
4. Type rcon "mp_fraglimit" "100"
5. Type rcon "mp_timelimit" "60"
6. Close console
Now you're running at 1/4 gravity (super long jumps), 100 kills, and one hour of play. By the way, if you wish to extend the timelimit, you have to add the additional time to the timelimit. To play 30 minutes longer, you change mp_timelimit to 90... not 30.
Poke around here
http://www.config-world.uklinux.net/cs/1.shtml or search out RCON COMMANDS in Google.