Over-simplification - all too often I seek the simplest answer that science can provide. Occam's razor is only a heuristic, not an answer.

Over-obfuscation - often I cloud myself with wordy rhetoric and eschew obfuscation. bad phil, bad. It makes me think I'm smart and novel. So don't accuse me of using big words to sound smart--really, what I am doing is unwittingly reading more profundity than exists.

Over-neutrality - sure just because there are two sides to every coin, doesn't mean one side can't be right and the other side wrong.

Over-relativism/agnosticism - (I actually don't do this, but I used to) - too often I used to pull out the "we can never know card" or "there is no right or wrong" card. Yes, ultimately the problem of "accuracy" is an unsettled debate in philosophy, but I should then be consistent. If I pull the "we have no idea" card, I have to make sure that this is a special case referring to an exceptional dearth of evidence... otherwise, then I should apply it to everything.

Over-emphasis on existential - I often use "might" or a "could"-happen as evidence that something WILL happen. Just because I think I could become a famous writer someday, doesn't mean I should walk around with the expectation/hope that I actually will become that way.