X-ray crystallography is the gold standard technique for the structural determination of biological macromolecules such as proteins, nucleic acids, viruses and their complexes. Much of our information in structural biology, in particular about proteins, come from X-ray crystallography studies. This dissertation covers different aspects of protein X-ray crystallography which is an inherently multifaceted tool with many adjustable experimental knobs. We present temperature, cooling rate and relative humidity dependence of protein structures which, when put together, offers a much more complete picture of protein structure, dynamics and function. We also quantify radiation damage to protein samples at cryogenic temperatures by establishing `local’ Fourier-space relationship between radiation damage and dose which is well supported by our simple physics-based model, yet very consistent with both diffraction and imaging experiments over more than two orders of magnitude in resolution, explaining the underlying mechanism.