The cmds.ini file in your addons/amx/config folder contains a list of commands that may be run from the Commands Menu. This is enabled by using the amx_cmdmenu command. This is what the default cmds.ini looks like:
(Note that a semi-colon ; was inserted at the beginning of some lines. This prevents them from being used.)
Adding commands to the menu for use should be entered as other commands are shown in this file. The difference between flags a and b is some commands may only work from the server's console and not the client's. Non AMX commands like "restart" for restarting the map must be run from the server console. You can use \' to replace a quote inside your command.
Here are some examples of how to add a vote command to the menu for Dust2, and a command for restarting the current map:
This menu is accessed in the game by typing amx_cmdmenu in the console. Or by binding a key to that command. The menu will show up on the left side of your screen while playing. It looks like this with the added commands from above:
Just select the number of the command you want to run and that's it. Any changes made to the cmds.ini file will show up after the next map change or server restart.