The regulations

Less than 2 miles
No flares
Coastal 2 to 6 miles
1 set of 3 SOLAS approved hand flares
Offshore, more than 6 miles
1 set of 3 SOLAS approved hand flares
3 SOLAS approved parachute flares
2 SOLAS approved smoke cannisters
(Flares and smoke are not mandatory if the boat is equipped with VHF DSC coupled with a GPS.)

Go beyond the regulations

Less than 2 miles from shelter no flares are obligatory. Do though, take at least 3 hand flares, a small investment that may prove useful to indicate distress. Between 2 to 6 miles, it is advisable to move toward a kit identical to that of navigation of at least 6 miles. Be aware that the three parachute flares and two buoyant smoke are no longer demanded if you have an onboard VHF DSC coupled with a GPS. This is an aberration! In case of problems, the responsibility of whoever is in charge onboard, should be inititated. Beyond 2 miles from a shelter you can complete your safety equipment with glow sticks (Cyalume), white anti-collision lights and pen rockets.

03_07_Boite Fusees

The proper use

To be identified: We use rocket flares which permits the guidance of rescuers to the distree location. The duration of visibility is short. For a rocket projected to 300 m, it is only 40 seconds, it is visible at night 20 miles (depending on conditions.)
For the approach: Once help is near (in view,) they may be guided accurately with hand  60 secoflares. The flame emits an intense red light fornds and is visible from 3 to 5 miles.
For hand flares (like rockets), always turn your back to the wind, the arms above the water and activate.
In case of winching: one activates the smoke when the helicopter is overhead and once opened it is thrown into the water. It lets off a dense orange smoke for about 3 minutes. This smoke allows the pilot of the helicopter to see the direction and wind speed at the water's edge.
Professional advice
“One must know and understand pyrotechnic equipment before use. Read the instruction before any emergency occurs and locate the opening direction, for when one must use it at night.”