Apart from the various astrological remedies practiced to awaken sleeping planets, I have given a generalized indicator, when and how a sleeping planet is most likely to be awakened.
Jupiter [Guru] - Will awaken the day when the native finds a job/employment or business and starts earning his own bread.
Sun [Ravi] - Will awaken when the native finds any kind of government employment or if he does some work for the government. This occurs normally after the age of 22.
Moon [Chandra] - Awakens when the native commences his education. If there is a break in the education then the native should restart his education after the age of 24, when the Moon reawakens.
Venus [Shukra] - If sleeping will awaken after the marriage of the native.
Mars [Mangal]-Will awaken after the age of 22, after marriage or after physical relation with the opposite sex.
Mercury [Budh] - Awakens after the age of 34 when the native starts his own business or after the marriage of the natives sister or daughter or if he does the ritual of Kanyadaan for any woman.
Saturn [Shani] - After the age of 36 or after the native builds his own house.
North Node [Rahu] - After the age of 42 or after the native comes close to his in-laws and has good relations with the in-laws,
South Node [Ketu] - After the age of 48 or after the native becomes a parent.