I know I said I would read the Bhagavad Gita and discuss my interpretations...and I won't let you down! So here at last, after what must've been an insufferably long time, are my thoughts on Chapter 3, which is on the topic of karma.
I have to admit - this chapter was a difficult one for me to read. I wasn't upset by any of it, it was just so dense and full of meaning (sometimes appearing contradictory to me at first) that it's hard for me to make heads or tails of it. Nonetheless, I shall make an attempt.
To me, this chapter seems to elaborate upon two key concepts as they relate to performing actions and the karma associated with them: mindfulness, and detachment. One thing this chapter says right away that I can definitely agree with is that we need to perform actions, we need to do things; in other words, we are born into this life to live it. There is no use shuttering away oneself from life's experiences, because they're the only way one can learn. Which brings me to one point I've just thought of in this regard, and that is one reason why we suffer: in the event we inflict it on others (sadly, we can't avoid it completely, sometimes it happens quite by accident), our suffering of the same event gives us an idea of what we've done. For example, I saw on this one TV show the process some police officers go through to get certified to use a taser, and part of it involves getting shot with a taser, so the officer knows how it feels! The idea is that it will (hopefully) encourage police to only use tasers when the situation really requires it. So in the event we do something to someone else, and haven't experienced it ourselves, karma makes sure that happens to us in one way or another. I think that is also why this chapter talks about the senses and mastery over them, in other words mindfulness. The senses are there to teach us what experience and action feel like, so therefore they aren't the end-all-be-all of existence. The senses are important, but we control our actions, not the senses.
That brings me to the next aspect of this chapter: detachment. I understand the principle of detachment and its benefits, as it can lead to altruism and selflessness. But there is the other side of the coin, where detachment can be used for evil. For example, if you're completely detached from the results of action, then one could conceivably do very bad things - what would stop you from committing murder if you weren't attached to the result? Ditto with doing things in the name of God: for every Mother Teresa there's an Osama bin Laden. (And yes, I know all religions, including Christianity, have infamous figures who have committed crimes against humanity in the name of religion. Osama bin Laden was just the easiest one I could think of.)
So if one's not supposed to be attached to the results of action, how does one know what's good and what's evil? That, I believe, is why Krishna invoked following the example of gurus. Gurus are supposed to be models in this regard, as Krishna himself said that if he were to partake in evil action, society would follow suit and collapse, etc. But again this can be problematic - many people who proclaim themselves as a guru of some sort all have different ideas as to what's good and what's evil. How do you know which gurus are good and which ones just want to brainwash their followers to commit evil for them?
The answer to that question, I believe, lies in self knowledge. Krishna invoked that aspect of being as a way of telling us to ultimately follow what our own experiences tell us is good or evil. That knowledge of self is supposed to tell one who to follow in action - that to know who is a true guru for oneself, one has to know oneself first.
There was a lot to sift through in chapter three...it took some considerable effort to come up with those conclusions and then connect the dots, so to speak. However, I hope my interpretation at least makes sense - chime in the Comments section with what you think, as always.