Moles have an excellent sense of smell and will avoid traps if the smell of humans. Before setting the traps wash them with rain water and leave them out to 'weather' for a few days to remove any 'human' smell.
Moles create two types of tunnel shallow and deep. It is the deep tunnels that they tend to use on a regular basis and this is where the traps should be set. To locate the tunnels work around fresh molehills pushing a thin bamboo cane into the surrounding soil. You will be able to feel when you have located a tunnel. Cut carefully into the tunnel and set the traps with the scissor prongs at the edges of the tunnel and closing into its centre.
For most of the year moles are solitary animals and so once you have caught a mole there is unlikely to be another close by, so the traps can be removed.
Unless the traps are in mole runs do not leave them set. Set traps could easily cause harm to children, pets and other non-target animals.