How to enable or disable snap termporarily

While moving the vertex..etc with G, during the move, hit CTRL and the snap will enable termporarily. If your snapped was enabled in the beginning, then press CTRL will disable the snap temporarily.

Choose the correct snap mode

Remember to be in the correct snapping mode while doing this. Like when you want to enable the snapping for vertex temporarily, make sure that the vertex option is selected in the snap toolbar.