Something important is to not underestimate... Really, sometimes I bump into some really ignorant religious people, but you may be surprised when someone who knows a lot about philosophy and science genuinely thinks a god exists and creates a more complex version of the cosmological argument that is not easy to debunk at first glance.
I try to keep personal insults out of debate with theists because I think it only creates antagonism between both groups. Generally spotting fallacies is not hard. When the theist is religious it is an easier task because you can simply ask the person why she/he doesn't believe in thor, zeus or hades instead. But when the theist is a liberal one, or a deist, or a pantheist, it is a bit more complicated and some arguments are unpredictable - Not to mention that as hard as it is to admit some atheist arguments do contain fallacies, though not enough to discredit atheism.
I try to keep personal insults out of debate with theists because I think it only creates antagonism between both groups. Generally spotting fallacies is not hard. When the theist is religious it is an easier task because you can simply ask the person why she/he doesn't believe in thor, zeus or hades instead. But when the theist is a liberal one, or a deist, or a pantheist, it is a bit more complicated and some arguments are unpredictable - Not to mention that as hard as it is to admit some atheist arguments do contain fallacies, though not enough to discredit atheism.
Whoever fights monsters should see to it that in the process he does not become a monster. And if you gaze long enough into an abyss, the abyss will gaze back into you
