I have clippers. I cut the spaniel's nails when necessary. Yet I am hesitating with the pup. His nails need trimming, but they are jet black so I can't see the quick. Is there some magical way of knowing how much to trim? I don't want to hurt the poor bugger. He's already put up with me randomly plucking his ears while he's distracted and somewhat suspicious of my intentions.
Definitely little and often. You might want to invest in a silver nitrate pencil just in case you accidentally nip the quick as this stops bleeding really quickly. Do be aware that it stains your skin though so avoid that.
Just take tiny slivers off at a time and as LabradorMama said, look from underneath to help you judge where the quick is. The more frequently you trim, the more the quick shrinks back, so it's a good idea to do it fairly regularly as, contrary to what you'd expect, it actually reduces the likelihood of nipping the quick.