You should get as close as possible. Many people use a sheet of paper as their gauge. I bought a cheap metric feeler gauge and I use the 0.02mm blade to set mine up.
1mm is always too high. You want it about .1mm or .2mm above the surface. Use the paper test: get a piece a paper and lower the nozzle until it touches on it, and gives an adequate amount of tug when you are pulling not he paper.
