A priori there are no core indicators
Indicators must be chosen on the basis of the hypotheses of the program
The "best" method is not necessarily the appropriate method (ie. The "gold standard" is a point of comparison not a given)
Field and analytical methods must be comparable in terms of precision
Analysis cannot compensate for poor experimental design
Design, sampling, analysis, and reporting need to be integrated
Quality control is a necessary component of any sampling program.