To set Mac OS X 10.5 (Leopard) to check for software updates daily, follow these steps:

1. From the Apple menu, click System Preferences.
2. In the System Preferences window, click the Software Update icon in the second to last row. This icon is circled in white in the following graphic:

   

You will see the Software Update window, which looks similar to the one below:

3. If a check mark is not already present, click in the checkbox in front of Check for updates.
4. From the drop-down arrow to the left of the field, select Daily.
5. If a check mark is not already present, click in the checkbox in front of Download important update automatically.