This topic will discuss the Law of Causality. If you understand the Law of Causality well then you are able to obtain enlightenment. If you use this method you are called a Causality Enlightenist.
Simply, the Law of Causality means that everything has a Cause and Effect. There cannot be one without the other. So when you do good deeds, good things will happen. Either in the present or in the future, perhaps even a future lifetime. This is what people mean when they are talking about Karma.
There is both personal karma and also group karma. Know that the Law of Causality is utterly fair. It is not biased in any way, and is the ultimate justice. All good you do and all bad you do have coresponding effects. If you experience difficulties it is a Karmic result of your past actions. This is a fundamental belief of Buddhism.
The Law of Causality basically states that every effect was generated by a cause. It is impartial and absolutely fair to everybody without differentiation.
So in previous lives, you lived your life and made certain decisions and took certain actions, these are causes. Some of the decisions and actions you took in previous lives would have had an immediate effect, some would have taken a short time to see the effect. Some decisions would take longer to see the effect. Then your lifespan in previous lives came to an end, everything was impartially reviewed (good and bad) and you were reincarnated as you deserved. The process is the same for everyone. When you are reincarnated you brought over the previous actions (good and bad) as well as causes which had not yet resulted in the effects being played out. (I.e., long term effects) (this is what is referred to as Karma specifically)
Some effects still need to play out. Think of actions/causes as deposits or withdrawls to your bank account, and your balance as your Karma. Those transactions have already taken place. What you can do to improve your Karma is to take actions now(make deposits), that will positively effect your Karma (bank account). Some of your positive actions will have immediate or short term effects, some will only resolve themselves after you have been reincarnated again.
The reason why good and bad things (effects) happen to people are because of causes, both in this life and your karma from previous lives. As the Law of Causality is utterly impartial and fair all causes generate effects and the effects play out for everyone without exception. You can also try to improve your situation by reading the Sutra's and doing as instructed in them. There are often specific actions you can take to help greatly mitigate specific poor actions in the past and it will say in the sutra in more detail.
For example the sutra might say something along the lines of, if in a past life you had done x, y ,z but now you might read, recite, understand, comprehend, uphold and relate even as little as a quatrain (4 lines) of this sutra to others then (positive benefits x, y, z listed)
How to deal with negative effects when they resolve themselves is to do either positive actions as expounded by the Buddha in Sutras or to Do Nothing. Doing Nothing is actually very powerful, not taking action is a kind of action. What you are really doing by not taking action is to Stoically take the full force of the effects of previous actions, and in doing so keeping in mind that it is just temporary and will pass. The doing positive actions approach is an attempt to mitigate to some degree the force of the effects you feel from previous actions. You might not be able to dodge All of the negative effects but you can greatly reduce it.
There is a link in the authorized books section where you can receive buddhist sutras translated by authentic monks. You might want to take a look at the Altar Sutra.
So to summarize if you do good things good stuff will happen, if you do bad things bad stuff will happen.



