  We present a quick-start guide to BOND, a statistical method to derive oxygen
and nitrogen abundances in H II regions. BOND compares a set of carefully
selected strong and semistrong emission lines to a grid photoionization models.
The first novelty, in comparison to other statistical methods, is that BOND
relies on the [Ar III]/[Ne III] emission line ratio to break the oxygen
abundance bimodality. In doing so, we can measure oxygen and nitrogen
abundances without assuming any a priori relation between N/O and O/H. The
second novelty is that BOND takes into account changes in the hardness of the
ionizing radiation field, which can come about due to the ageing of H II
regions or the stochastically sampling of the IMF. We use the emission line
ratio He I/Hb, in addition to commonly used strong lines, to constrain the
hardness of the ionizing radiation field. Finally, we also stress the pragmatic
considerations behind our Bayesian inference.
