Sample spinning helps to remove X and Y shimming imperfections.  This will improve resolution for routine 1D 1H and 13C spectra.  For any other advanced experiments, spinning is not recommended as it might introduce artifacts into your spectra.

When running routine 1H or 13C spectra, if the sample does not spin, you might want to touch up X and Y shims in addition to Z and Z2.  Please note that topshim for 400 only corrects Z – Z4 shims.  So, after topshim, if the lock still seems noisy, touch up X and Y.  Higher order transverse shims (XZ, YZ, XY etc) usually do not markedly affect resolution.