Lots of good advice so far. I'd add that it's actually easier to land on grass, all other things being equal. The surface has a texture which allows height during the flare to be more easily judged, and as someone else pointed out, if you are not quite aligned with the runway at the point of touchdown, the wheels will slide a tad sideways and no-one will know, whereas on tarmac there will be a telltale chirp of tortured rubber, and a lurch as the aeroplane is dragged straight by the tyres!
SSD