Ax, karmas do not lead to liberation. If you perform an action, due to the law of causality(karmic law) that action will have an effect. This effect could either be positive or negative and it could be active or dormant. As soon as we perform an action it leaves a residue in the mind(samkaras) and then that like a seed germinates in the unconscious. This effect can be felt in this life or the next life, sometimes the karma can remain dormant for several lifetimes, it only manifests when it is triggered by a suitable environment. An example could be suppose you have a really bad experience at a certain place, this leaves a residue karma in your mind. Now, suppose for a few years you have forgotten about that bad experience. The karma remains dormant for these few years. However, you may visit that place again, and all of a sudden the karma is active again.
Another case could be you cause somebody harm in the past, let us say you hurt someone really bad by saying something to them. The karma you perform leaves a residue which enters your unconscious. It may lay dormant for a few years, but actually that seed is germinating in your unconscious, the karma may eventually cause you to end up bumping into that person again after several years. It may seem like a coincidence, but actually it is determined by your past karmas.
Another type of karma is that which determines the outcomes in your life. Some people seem to have all the luck, this is not random chance convergence, they genuinely do have good luck because of good karmas in the past. They may have been very charitable in their earlier years, and later on they get an unexpected inheritance worth a fortune.
At death, the breath detaches from the body, and the mind detaches from the breath and it takes its karmas with it. However, as long as it has unfulfilled karmas they create vasanas(desires) and long as it has desires it cannot be liberated from the cycle of birth and death. It can only fulfill those desires through a body, and therefore again it reincarnates. The kind of body it reincarates in, which time and place and the kind of life is all determined by the past karmas.
It does not matter which karmas you do, whether they are charity or theft, you will continue to reincarnate over and over again. The only difference is if you did good actions you will lead a relatively better life than if you did bad actions. The only way to become liberated is to reach a state of desirelessness. As soon as you have no desires left, you will merge into the supreme being. The only way to do this is through Yoga. In Sikhism this is through Bhakti Yoga, absolute devotion to god and always uttering his name(Sat Naam, Waheguru) so you allow yourself to become the instrument of god's will losing all sense of egoity and desire. In this state you will do good things like charity, service, teaching others, but you will not create any karmas, because you are simply doing his will. This is why Arjuna did not incur any bad karma when he carried out the will of Lord Krishna, despite engaging in murder and deceit. As soon as you surrender your 'I' to god, you become free of causality.
