If you always get equal marks in all subjects then give one hour to each one .
If it is otherwise, then in which subjects you feel , need more study give two hours .
In first go you read everything in detail regularly .
Leave all other activities.
In 2nd go give a quick reading.
But the points which are really important like. Dates, numbers, definitions . Learn them by writing again & again . To learn by heart .
When you start study say Bismaillah & when you finish say thanks to Allah