What is the proper way to apply subflooring to floor joist's when they change direction. Do you continue with the same pattern or do you change the direction of the subfloor pattern to match the joist change? And if you do what is the proper way to make the change?

Normally the plywood grain should be at fight angles to the joists no matter where they lie. There may be a transitional area but normally that is the rule of thumb. Check building codes in your area for exact details especially if there is any question of a lessening of stability from their position. MJH