The Karmas are of three types :
Sañcita -- Accumulated over countless previous Births
Prarabdha -- Which has to be necessarily experienced in this Birth
Agami -- Produced now due to Current Karmas to be experienced in future.
There is always the concept of limited applicability of freewill as well. By doing Prayascitta Karmas it is possible to mitigate the ill-effects to some extent.
Karma phalas are of three types Papa, Punya and Misra (Mixed).
If an action is done without attachment to its result, it does not bind the doer.
The Yuga dharma also influences a person in his actions.