Just re-execute the script file (using your console). If you're needing to execute a file in your add-ons folder use setmodpaths(getmodpaths());
ex:
setmodpaths(getmodpaths()); exec("add-ons/server_myadd-on/server.cs");
If the script has some datablocks that you're editing, call transmitdatablocks();
Some things, such as changing certain datablock properties require you to restart the server though.
Edit: wait i thought this was the modification discussion board.... oh well..