The concept of thinking in levels in poker is well known and well documented. A great many poker books and many websites cover it. This post isn't to describe thinking in levels. This subject is something that I've always had a bit of trouble organizing, especially past level one.
By that I mean am I thinking about his hand or my hand? or what's the difference between level 2 and level 3 thinking. or what level is I think that he thinks reasoning. I've found that this "I think that he thinks ..." and mapping that to levels quickly gets confusing and requires a lot of effort to me.
Now it has finally become a bit more organized to me and some patterns have emerged which I will describe here. First the levels in a more ad hoc way.
level 0 realizing what I have
level 1 thinking about what the other guy has
level 2 thinking about what the opponent thinks I may have
and so on
ok I found that by expressing the levels as questions to yourself some patterns start to emerge which simplifies things and helps to scale to higher levels
level 0 what do I have?
level 1 what does he have?
level 2 what does he think I have?
level 3 what does he believe I think he has?
the even numbered levels 0,2,4 ... are egocentric. it's about my hand, and what the opponent thinks I may have
the odd numbered levels 1,3,5 ... are extroverted. it's about figuring out villain's hand, and what opponent thinks the other players believe he has.