What should I do to ensure that my watch continues to provide excellent service for many years?

Magnetic fields: avoid placing your watch on electronic units, which can generate powerful magnetic fields.
Swimming in the sea: always rinse your watch with warm water afterwards
Shocks: whether thermal or other, avoid them.
Screw-in-crown: screw down the crown carefully to prevent water from penetrating the mechanism. 
Non screw-down crown: push it back into the neutral position to prevent water from penetrating the mechanism.
Cleaning: for metal bracelets and water-resistant cases, use a toothbrush with soapy water and a soft cloth for drying.
Chemical products: avoid direct contact with solvents, detergents, perfumes, cosmetic products etc., since they may damage the bracelet, the case or the gaskets.
Temperatures: avoid extreme tem peratures above 60°C or 140°F below 0°C or 32°F or extreme temperature changes.
Water resistance: A watch’s water resistance cannot be permanently guaranteed. It may be affected by the ageing of gaskets or by an accidental shock to one of the components assuring the water resistance such as crown, pushers and crystal.
As stipulated in our service instructions, we recommend you have the water resistance of your watch checked once a year by an approved service center.
Chronograph push-pieces: Do not operate chronograph pushers under water in order to prevent water entering the mechanism.
Power reserve (automatic) : the self-winding of the movement is generated by the motions of the wearer’s wrist. Since the watch’s self-winding mechanism (rotor) is directly linked to the wearer’s activity, 10 – 12 hours’ wear are sufficient to generate a power reserve and ensure that the watch continues to run throughout the night. Therefore, the watch should be worn 10 – 12 hours per day (normal daily activity) and this during several days. If the watch is not worn sufficiently (not long enough or without enough movement of the wrist) or not regularly (not on a daily basis), the power reserve will continue to drain requiring the watch to be wound manually. The crown will need to be wound manually 15 – 20 times to develop a sufficient power reserve and to ensure the accuracy of the timepiece. This simple procedure should be followed upon receiving a new mechanical watch and also be applied for a watch that is not running or that was not worn on a regular/daily basis. Please note that a common misconception is that by simply shaking an automatic watch, sufficient motion will be afforded to enable the watch to maintain accurate time. However, this procedure will neither wind the mainspring sufficiently nor establish a power reserve, ultimately causing the watch to stop or to track time inaccurately.
Leather strap: Our technical recommends that you follow the steps below in order to preserve the condition of your leather strap as long as possible:

1. Avoid contact with water and dampness to prevent discoloration and deformation.
2. Avoid prolonged exposure to sunlight to prevent the color from fading.
3. Do not forget that leather is permeable! Therefore avoid contact with greasy substances and cosmetic products. It is not advisable to clean your strap with leather cleaners.