How does the force of ones karma determine where the mind stream goes? &quot;On the other hand, superior Bodhisattvas, who have attained the path of seeing, are not reborn through the force of their karma and destructive emotions, but due to the power of their compassion for sentient beings and based on their prayers to benefit others. They are able to choose their place and time of birth as well as their future parents&quot;.
-- Reincarnation by The Dalai Lama 

So Superior Bodhisattvas can choose where to take rebirth, but the rest of us can't. So, what chooses where the rest of us get to take rebirth?
How does &quot;the force of karma&quot; determine where the mind stream goes after physical death?
In the case of the Bodhisattvas, is it their mind stream that makes the choice? And when they make this choice, do they choose from available alternatives and just pick what suits them best or do they have the power to create their ideal rebirth?
This question is very similar to another: Does Mahayana Buddhism discourage attaining enlightenment under the Gautama Buddha Sasana? In my answer to that question I explained how the bodhisatva who post-pones enlightenment developed. 


  How does "the force of karma" determine where the mind stream goes after a physical death?


Many different answers have been proposed and adopted by Buddhists of different schools at different times to try to account for how karma determines where the mind stream goes after death. But no one really knows. We say that this is what happens, but a satisfactory explanation of the process is entirely lacking. We sometimes use analogies to try to explain, but they don't really tell us anything about the reality of this process. 

The bodhisatva choosing their rebirth is simply an article of faith.