Know your system's lattice parameters and angles, and it's symmetry. Decide about the sample orientation - you get only one plane
Create hkl-intensity-list (reflection list). –> info about forbidden reflections and the (relative) intensities of the allowed. - Have it available for starting the experiment.
Mark the crystal direction on the sample holder
Mount the sample properly. Think about covering the glue or holder and about either fixing the sample by Al wire or mounting an Al foil bag around.
Mark the crystal direction outside on the cryostat
For magnets, sample mounting needs to be better than within 1°. Depending on the instrument, care that one crystal direction is parallel to the goniometer axis.
Start experiment. Experiment name, sample name, give sample metadata to system
Align the sample