If you plan on storing your Swiss dive watch for an extended period, like the IWC Aquatimer above, make sure to tighten the crown first. This will keep out any moisture or dust that might be in the air, and prevent damage to the seals that might compromise water resistance next time you go for a dip.
Watch lubricants will gradually dry out over time so it is important to get your watch serviced periodically at the recommended intervals (generally every five or six years). Some people recommend periodically winding an automatic watch to keep the internal mainspring from deteriorating.
If you plan on storing a quartz watch for more than a year, then you should probably remove the battery first since dead batteries occasionally leak and can harm the movement.