Level of thinking

[Restlys]

Simple question, what is the level of thinking, in general,of NL 5/10c players out there
Zeroth: what i have
1st: what i think he has
2cnd: what i think he thinks i have
3rd: what i think he thinks i think he has
etc

Im reading some theory about the concept in No limit Holdem: Theory and practice and was wandering what was the best level to be or other ways to determine which one best applies to a situation