This is especially important if you’ve got separated regions. Using tools such as reintson and reintsom to interpolate existing solutions to different grids can save you massive amounts of simulation time. These can also be used to extrude a 2D solution into 3D. I had problems with this option for axi-symmetric geometries (the Cartesian “nearest neighbour” approach doesn’t work very well for such things) so used the “cdeps1asn” tool to create a restart file from an ascii file that I generated myself that contained the x, y, z, P, T, U, V, W data.
If you don’t have an existing solution then initiating the domain using the XYZ boxes option to prescribe, for instance, zero velocity at the leading edge and a pseudo-recirculation bubble etc can also be a big help.
Another useful tool is the equation set convert option in the physics menu. You can use this to convert a laminar run to a turbulent run etc and then perform a restart.