The single hardest bias to avoid is the bias blind spot, wherein people think (maybe not overtly, but on a gut level) that they are less biased than other people.

I've never found any studies, papers, web pages, anecdotes, or anything at all on how to fix it, so I don't really know what to do about it. I have a conjecture, though, which intuitively appears that it might work (but take it cum grano salis):

To avoid bias blind spot, think "What biases are going into this decision?" every single time you make an important decision or come to an important conclusion. Then actually correct for them.

The problem with this is that people who currently take into account biases in their decisions (i.e. Less Wrong, and psychologists) end up not knowing how much their decisions are affected by the bias, and consequently they don't know how much to adjust. So they don't adjust at all. It ends up being an, "Okay, something's wrong here, but I can't fix it, so I'll just do the same thing I was going to do before," scenario.