organized by 350.org there are events all over the world. The significance of 350 is that it is the safe level of CO2 in the atmosphere. We are already at 390ppm, which is why the climate is changing and extreme weather events are becoming common. The level is going up by 2ppm a year at the moment and the changes needed to reverse this haven't started, so its going to go much higher and have increasingly worse effects.
Even if all you do is buy and start reading a copy of James Hansen's book Storms of my Grandchildren (you can get it instantly from the Kindle store) it will help.
Here is a useful discussion of "The Value of Coherence in Science" which is how you can tell what makes sense from what must be wrong. I'm a Physics graduate, and I was taught that science works by making predictions and testing them, and by eliminating incoherent propositions. i.e. if an argument contradicts itself it must be false. The denialist counter-arguments fail this test. To see why the denialist arguments are getting any air time at all, read Merchants of Doubt and Climate Cover Up.
For an example of incoherent and shoddy denialist work John Mashey has systematically deconstructed the Wegman Report which was presented to Congress as an impartial study when it was nothing of the sort.