  A substantial fraction of the time that computational modellers dedicate to
developing their models is actually spent trouble-shooting and debugging their
code. However, how this process unfolds is seldom spoken about, maybe because
it is hard to articulate as it relies mostly on the mental catalogues we have
built with the experience of past failures. To help newcomers to the field of
material modelling, here we attempt to fill this gap and provide a perspective
on how to identify and fix mistakes in computational solid mechanics models. To
this aim, we describe the components that make up such a model and then
identify possible sources of errors. In practice, finding mistakes is often
better done by considering the symptoms of what is going wrong. As a
consequence, we provide strategies to narrow down where in the model the
problem may be, based on observation and a catalogue of frequent causes of
observed errors. In a final section, we also discuss how one-time bug-free
models can be kept bug-free in view of the fact that computational models are
typically under continual development. We hope that this collection of
approaches and suggestions serves as a "road map" to find and fix mistakes in
computational models, and more importantly, keep the problems solved so that
modellers can enjoy the beauty of material modelling and simulation.
