The regular service indicator light on the dashboard of your Laguna II (2001 on) will come on every 18,000 miles and the distance to the next service will be blank.
To reset :

• Toggle through to the service display.
• Press the mileage counter reset button  - the one below the speedo.
• Hold for 5 secs.

The display will be reset to 18,000 miles and the service light will go out.
You will, of course, have performed all the required maintenance tasks. In particular, it is recommended that you do the following more frequently than Renault suggest:

• Oil & filter change - every 10,000 miles
• Cam belt - every 40,000miles.

Note that this only applies to the service light coming on at the regular service interval. The light will stay on if it is illuminated for any other reason, e.g. tyre pressure, until you fix the problem.