The first step in understanding constitutional principles is to have an understanding of the constitution itself. Examine it here: http://www.usconstitution.net/const.html
Get your own personal pocket sized copy of the constitution go here: https://secure.heritage.org/firstPrinciples/pocketconstitution.aspx?gclid=CL_nnLKt3pcCFRyenAodlWcsDQ